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Unit 7 EXAM Thermodynamics, Kinetics and Equilibrium

Unit 7 Interactive Notebook Score Sheet

Quizzes/Formatives Date Score/Max Score

Retake Needed (yes or no)

Peer Initial Parent Initial

Formative 29 Specific Heat Thermochemistry

Formative 30 Phase Diagrams

Formative 31 Potential Energy Diagrams

Formative 32Kinetics

Formative 33 Equilibrium

Unit 7 Test

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Name of Scored Assignment Date Due Score/Max Peer Initials Level of Effort

HW Quiz 7-1 Heat Transfer/Conversions

HW Quiz7-2 Sp.Heat Eq. and Graph

HW Quiz 7-3 Phase Diagrams

HW Quiz 7-4 Potential Energy Diagram

HW Quiz 7-5 Kinetics Vocab/Graph

HW Quiz 7-6 Equilbrium Eq/Graph

HW Quiz 7-7 Le Chatelier’s Principle

Graphing Heating Curve for Water

Graphing Reaction Rates

Bell Work

Unit 7 Interactive Notebook

Histograph Graph – Date (x axis) and progress on standards mastery with 5 advanced, 4 proficient, 3 basic, 2 below basis, and 1 incomplete (y axis)

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California Chemistry Standard Chemical Thermodynamics.7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. 7. a. Students know how to describe temperature and heat flow in terms of the motion of molecules

(or atoms). Temperature is a measure of the average kinetic energy of molecular motion in a sample. Heat is energy transferred from a sample at higher temperature to one at lower temperature. Often, heat is described as flowing from the system to the surroundings or from the surroundings to the system. The system is defined by its boundaries, and the surroundings are outside the boundaries, with “the universe” frequently considered as the surroundings.

7. b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.Endothermic processes absorb heat, and their equations can be written with heat as a reactant.

Exothermic processes release heat, and their equations can be written with heat as a product.

The net heat released to or absorbed from the surroundings comes from the making and breaking of chemical bonds during a reaction. Students understand and relate heat to the internal motion of the atoms and molecules. Breaking a bond always requires energy and that making a bond almost always releases energy. The amount of energy per bond depends on the strength of the bond.

The potential energy of the reaction system may be plotted for the different reaction stages: reactants, transition states, and products. This plot will show reactants at lower potential energy than products for an endothermic reaction and reactants at higher potential energy than products for

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an exothermic reaction. A higher energy transition state usually exists between the reactant and product energy states that affect the reaction rate.

7. c. Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts. Physical changes are accompanied by changes in internal energy. Changes of physical state either absorb or release heat. Evaporation and melting require energy to overcome the bonds of attractions in the corresponding liquid or solid state. Condensation and freezing release heat to the surroundings as internal energy is reduced and bonds of attraction are formed.

7. d. Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change. Specific heat is the energy needed to change the temperature of one gram of substance by one degree Celsius. The unit of specific heat is joule/gram-degree. During phase changes, energy is added or removed without a corresponding temperature change. This phenomenon is called latent (or hidden) heat. There is a latent heat of fusion and a latent heat of vaporization. The unit of latent heat is joule/gram or kilojoule/mole. Students should be able to diagram the temperature changes that occur when ice at a temperature below zero is heated to superheated steam, which has temperatures above 100°C.

California Chemistry Standard Kinetics - Reaction Rate 8. Chemical reaction rates depend on factors that influence the frequency of collision of reactant molecules1

The rates of chemical reactions that consume reactants and form products are affected by several factors: temperature, pressure, and concentration. Chemical reactions can be explained at the molecular level where kinetic energy at the molecular level is measured by temperature. An important way of describing the potential energy is to plot potential energy versus course of reaction for endothermic and exothermic reactions. The rates of change can be calculated from slopes of lines on the potential energy graph. Steep lines have reactions that are fast.8.a. The rate of reaction is determined by measuring the decrease in concentration of reactants or the increase in concentration of products with time. Qualitative knowledge of the reaction rate measures how fast reactions proceed and general scales of rate: explosive and biological/cellular reactions are very fa st, while rusting (iron oxidation) is very slow. Reaction rate is defined as the rate of decrease in concentration of reactants or as the rate of increase in concentration of products, and these changes form a balanced equation (mole ratios) that reflects the conservation of matter. Conservation of matter means that the total mass does not change.8.b. Reaction rates depend on such factors as concentration, Concentration, temperature, and pressure are major factors affecting the collision of reactant molecules and, thus, affecting reaction rates. Increasing the concentration of reactants increases the number of collisions per unit time. Increasing temperature (which increases the average kinetic energy of molecules) also increases

the number of collisions per unit time. The greater kinetic energy dramatically increases the chances of each collision leading to a reaction. Collisions have more energy to overcome the activation energy barrier.

Increasing pressure increases the reaction rate only when one or more of the reactants or products are gases. With gaseous reactants, increasing pressure is the same as increasing concentration and results in an elevated reaction rate.

1 http://www.chemguide.co.uk/physical/basicratesmenu.html#top6

Additionally, the surface area of the reactants affect the rate with pulverized powders being more reactive than lumps or chunks.8.c. Catalyst increasing the reaction rate. A catalyst increases the rate of a chemical reaction without taking part in the net reaction. Catalysts speed up rates by lowering the activation barrier along the reaction pathway between products and reactants. A catalyst lowers the energy barrier, activation energy, between reactants and products by promoting a more favorable pathway for the reaction. Surfaces often play important roles as catalysts for many reactions. One reactant might be temporarily held on the surface of a catalyst. There the bonds of the reactant may be weakened, allowing another substance to react with it more quickly. Living systems speed up life-dependent reactions with biological catalysts called enzymes. Enzymes are proteins that are made from amino acids. Catalysts are not consumed in the reaction, they are reused. Catalysts are used in automobile exhaust catalytic converters to reduce the emission of smog-producing unburned hydrocarbons. 8.d.* Reactants are usually required to pass through a transition state that has a higher energy than either the reactants or the products. The additional energy, called the activation energy, or the activation barrier, is related to such factors as strength of bonding within the reactants. The more energy required to go from reactants to activated transition complex, the higher the activation barrier, and the slower a reaction will be. California Chemistry Standard Chemical equilibrium is a dynamic state. Changes in heat accompanying chemical reactions and spontaneity of chemical reactions are key topics necessary to identify physical states of substances undergoing chemical reactions. Students need to know:How gases respond to changes in pressure and volume. How to calculate concentration and molarity for solutions, particularly for aqueous solutions. How to write acid–base reactions and precipitation reactions. How to calculate equilibrium constants, How to balance chemical equations, How to work readily with concentration and pressure units, and use mathematical exponents.Equilibrium, a dynamic process, with no net changes in a product or reactant concentration. An

analogy can be made with a pair of escalators operating between two floors. If the same number of people go up as go down in a ten-minute interval, the rate of people

moving up equals the rate of people moving down. Overall, any extra people arriving on one floor are canceled out by others leaving the floor. Therefore,

the number of people on each floor will be constant over time, and the population of the two floors is in dynamic equilibrium. This analogy can be extended to a chemical reaction by considering that if the number of moles

produced in one direction of the reaction is the same as the number consumed in the opposite direction, then the reaction has reached a state of dynamic equilibrium. When a stress is applied to a chemical reaction in equilibrium, a shift will occur to partly relieve the stress.9. a. Students know how to use Le Chatelier’s principle to predict the effect of changes in concentration, temperature, and pressure. If an equilibrium system is stressed or disturbed, the system will respond by changing or shifting to partially relieve or undo the stress. A new equilibrium will eventually be established with a new set of conditions. When the stress is applied, the reaction is no longer at equilibrium and will shift to regain equilibrium. For instance, if the concentration of a reactant in a reversible reaction system in dynamic equilibrium is decreased, products will be consumed to produce more of that reactant. Remember that heat is a reactant in endothermic reactions and a product in exothermic reactions. Therefore, increasing temperature will shift an endothermic reaction to the products side on the right to regain equilibrium. Note that any endothermic chemical reaction is exothermic in the reverse direction.Pressure is proportional to concentration for gases; therefore, for chemical reactions that have a gaseous product or reactant, pressure affects the system as a whole. Increased pressure shifts the equilibrium toward the smaller number of moles of gas, alleviating the pressure stress. If both sides

of the equilibrium have an equal number of moles of gas, increasing pressure does not affect the equilibrium. Adding an inert gas, such as argon, to a reaction will not change the partial pressures of the reactant or product gases and therefore will have no effect on the equilibrium.

9. b. Students know equilibrium is established when forward and reverse reaction rates are equal. Forward and reverse reactions at equilibrium are going on at the same time and at the same rate,

causing overall concentrations of each reactant and product to remain constant over time.9. c.* Students know how to write and calculate an equilibrium constant expression for a reaction.

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Because the concentrations of substances in a system at chemical equilibrium are constant over time, chemical expressions related to each concentration will also be constant. Here is a general equation for a reaction at equilibrium: aA + bB ↔ c C + d D

The general expression for the equilibrium constant of a chemical reaction is Keq, defined at a

particular temperature, often 25°C. Its formula is[ Cc ] [Dd ][ Aa ] [ Bb ]

=ProductsReac tan ts

When Keq is being calculated, only gaseous substances and aqueous solutions are considered. Solids or liquids are not included because it is assumed that their concentrations are unlimited. Equilibrium concentrations of products, in moles per liter, are in the numerator, and equilibrium concentrations of reactants are in the denominator. The exponents are the corresponding coefficients from the balanced chemical equation. A large Keq means the forward reaction goes almost to completion; that is, little reverse reaction occurs. A very small Keq means the reverse reaction goes almost to completion, or little forward reaction occurs. The solubility product constant Ksp is the equilibrium constant for salts in solution.

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Unit 7 Thermochemistry, Kinetics, and Equilibrium March 28, 2014-May 6, 2014Glencoe Chemistry Chapter 16, 17, and 18Thermochemistry CA Standards 7a. Students know how to describe temperature and heat flow in terms of the motion of molecules. Kinetic theory

of heat and temperature.b. Students know chemical processes can either release energy

(exothermic) or absorb (endothermic) thermal energy.c. Students know energy is released when a material condenses

or freezes and is absorbed when a material evaporates or melts.

d. Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.

Kinetics CA Standards 8 Chemical reaction rates depend on factors that influence the frequency of collision of reactant molecules.a. Students know the rate of reaction is the decrease in concentration of reactants or the increase in concentration of

products with time. b. Students know how reaction rates depend on such factors as concentration, temperature, and pressure.c. Students know the role a catalyst plays in increasing the reaction rate.d.* Students know the definition and role of activation energy in a chemical reaction.

Equilibrium CA Standards 9 Chemical equilibrium is a dynamic process at the molecular level. a. Students know how to use Le Chatelier’s principle to predict the effect of changes in concentration, temperature,

and pressure. b. Students know equilibrium is established when forward and reverse reaction rates are equal.c.* Students know how to write and calculate an equilibrium constant expression for a reaction.

Key Vocabulary TermsThermochemistry Kinetics EquilibriumHeat (Thermal Energy) Collision Theory Le Chatelier’s PrincipleTemperature Effective Collisions EquilibriumHeat Capacity Catalysts Reversible EquationsExothermic Enzymes Irreversible EquationsEndothermic Lock and Key Model Dynamic EquilibriumHeat of reaction Activation Complex ShiftLatent Heat of fusion Activation Energy StressLatent Heat of vaporization Reaction Rate Forward vs. Reverse ReactionsPotential energy Rate QualitativeKinetic energy QuantitativeJoulesCaloriesCalorimeterEnthalpy ∆HEnergy DiagramsSpecific Heat

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Concepts1. The phase changes that require energy and those that release energy

2. Collision Theory explains why reactions occur and how the rates of chemical reactions can be modified and the effects of orientation and activated complex on rates

3. Factors affecting reaction ratesa. Nature of reactantsb. Concentrationc. Surface aread. Temperaturee. Catalysts f. Inhibitors

4. Explain how catalytic converters work to reduce air pollutants in vehicle exhaust5. Explain reversible and non-reversible reactions6. Le Chatelier’s Principle of equilibrium shifts in response to concentration [M], temperature, volume, and

pressure for gases7. Explain the Haber process and Le Chatelier’s Principle

Items for Memorization1. Reaction rate is defined as the rate of decrease in

concentration of reactants or as the rate of increase in concentration of products

2. Equilibrium Constants qualitative expressionsKeq = 1 neither reaction direction favoredKeq > 1 means forward reaction favoredKeq<1 means reverse reaction favored

Skills1. Know when to use the three different general Calorimetric Formula and Constants for water (Chemistry Reference

Sheet)

No phase change: Q=mCp∆T

Latent Heat of Fusion when melting/freezing: Q=m∆Hfus

Latent Heat of Vaporization when boiling/condensing: Q=m∆Hvap

2. Q=mCp∆T Solve for heat (Q), mass (m), specific heat (Cp), change in temperature (∆T), beginning or ending temperature

3. When interpreting phase change graph. Given a point on a phase change diagram determine whether the state was solid, liquid, or gas.

Know and locate what the triple point means

Know and locate the critical point means

Normal boiling pointNormal melting point

4. Unit conversion: 1cal = 4.18J

5. Write chemical equilibrium expressions [products]/[reactants] and calculate Keq

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6. Write dissolution reactions as solubility expressions and use Ksp (solubility product constants)INTRODUCTION TO ENERGY2 Practice Classifying Part 1. The two basic types of energy Directions: Determine the best match between basic types of energy and the description provided. Put the correct letter in the blank.

______1. A skier at the top of the mountain (a) Kinetic Energy

______2. Gasoline in a storage tank (b) Potential Energy

______3. A race-care traveling at its maximum speed (c) Both forms of Energy

______4. Water flowing from a waterfall before it hits the pond below

______5. A spring in a pinball machine before it is released

______6. Burning a match

______7. A running refrigerator motor

Part 2. Definitions of Energy.Directions: Write down the definition for each of the following terms after reading the article.

ENERGY:

How does potential energy and kinetic energy differ?

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_____________________________________________________________________________________

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Directions: Match the energy form(s) to the description provided. _____________1. Falling rocks from the top of a mountain (a) Mechanical

_____________2. Release of energy from the Sun (b) Electrical

_____________3. Energy released from food after it is eaten (c) Heat

_____________4. Batteries (d) Radiant

_____________5. The energy that runs a refrigerator (e) Chemical

_____________6. Nuclear fission reactors (f) Nuclear

_____________7. The rumble of thunder from a storm (g) Sound

_____________8. Rubbing your hands together

_____________9. Gasoline

_____________10. Food before it is eaten

_____________11. Lightening2 http://pasambag.ism-online.org/files/2011/11/INTRODUCTION-TO-ENERGY.docx11

Chapter 16 Energy and Chemical ChangeEnergy is the ability to do work or produce heat.Law of Conservation of Energy = First Law of Thermodynamics

Two Forms of Energy 1. Potential Energy

2. Kinetic Energy K.E. = 1/2 mv2

Summary

Form Definition Type (KE, PE, or Both)

Example (for each type if both)

Mechanical (motion) energy

An object’s movement creates energy

Thermal (heat) energy The vibration and movement of molecules

Radiant energy Electromagnetic waves

Electrical energy Movement of electrons

Chemical energy Stored in bonds of atoms and moleculesNuclear energy Stored in the nucleus of an atom; released

when nucleus splits or combinesSound energy Vibration of waves through material

Gravitational energy Energy of position or height

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Heat FlowsTemperature is a measure of the average kinetic energy of molecular motion in a sample. Heat is energy transferred from a sample at higher temperature to one at lower temperature. Often, heat is described as flowing from the system to the surroundings or from the surroundings to the system. The system is defined by its boundaries, and the surroundings are outside the boundaries, with the universe, frequently considered as the surroundings and the system. System: Whatever we’re studying. This can be practically anything. If we are studying what happens when

we heat a pan of water on the stove, the pan of water will be the system we are studying.

Surroundings: Everything outside the system. When studying the pan above, the surroundings will primarily consist of

the stove (because it’s putting energy into the pan), though it technically consists of everything but the pan.

Universe: The system + the surroundings. In a general, the universe consists of everything

that exists anywhere. From a thermodynamic standpoint, the universe usually consists of whatever the system we’re referring to is as well as whatever is putting energy into or taking energy away from it.

Example: If we’re studying a space heater, the heater will be our system, the house will be our surroundings, and the universe will be the heater and the house together.

ENDOTHERMIC AND EXOTHERMIC PROCESSES If a system gets energy added to it, the amount of energy it

has after the change is positive. Because of this, an endothermic process is any process in which energy is absorbed by the system we’re talking about.

If a system has energy taken away from it, the amount of energy it has after the change is negative. Because of this, an exothermic energy is any process in which energy is given off by the system we’re talking about.

Chemical Processes Endothermic processes absorb heat, and their

equations can be written with heat as a reactant. Breaking a bond always requires energy

Exothermic processes release heat, and their equations can be written with heat as a product. making a bond almost always releases energy

The net heat released to or absorbed from the surroundings comes from the making and breaking of chemical bonds during a reaction. The potential energy of the reaction system may be plotted for the different reaction stages: reactants, transition states, and products.

Chapter 16 Energy Transfer and Transformationchemical processes either release (exothermic) or absorb (endothermic) energy

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∆H =Hfinal - Hinitial

∆H is Enthalpy

-∆H is

+∆H is

Heat Flow Heat is the transfer of thermal energy from an object at a higher temperature

to an object of lower temperature.

Calorimetry – measures

Heat flow for chemical

And physical processes

Conductors

Insulators

Energy Terms Challenge3

Definition TermA. the capacity of a physical system to do work 1. _____ atomB. energy that is carried through the electrons or protons of atoms 2. _____ chemical energyC. everything that has mass and occupies space 3. _____ electrical energyD. the smallest complete unit of a compound; a combination of atoms joined by covalent bonds

4. _____ electron

E. energy that an object has because of its motion 5. _____ energyF. energy that is released in a nuclear reaction either by fusion or fission

6. _____ kinetic energy

G. a process in which stars give off light and heat; the joining of two nuclei together into one, which releases great amounts of energy in the form of heat and light

7. _____ matter

H. the smallest part of an element that has all of the chemical properties of that element

8. _____ molecule

I. energy that an object has because of its position 9. _____ nuclear energyJ. a subatomic particle inside the nucleus of an atom; it has positive electric charge

10. _____ nuclear fission

K. the splitting of a nucleus of an atom nuclei of a heavy element, induced by the absorption of a neutron; it releases a large amount of energy

11. _____ nuclear fusion

L. energy that is transferred by rays, waves, or particles; its transfer between objects does not require a medium; also known as radiation

12. _____ nucleus

3 http://www.ignitelearning.com/science/Energy.pdf14

M. a negatively charged particle found in regions around an atomic nucleus

13. _____ potential energy

N. energy associated with heat 14. _____ protonO. energy stored in the chemical bonds of molecules 15. _____ radiant energyP. the positively charged and central part of an atom where most of its mass isconcentrated

16. _____ thermal energy

7d Standard: Students know how to solve problems involving heat flow and temperature changesEnergy Conversion Problems

Convert 200 cal to Joules Convert 25.10 Joules to calories

Convert 334.4 Joules to calories Convert 150 calories to Joules

Specific Energy Problems Equation for No Phase Change Q = m (∆T) Cp1) Solve for Q 2) Solve for mass 3) Solve for ∆T 4) Solve for Cp

Change in Temperature Problems∆T = Tfinal - Tinitial

1. to raise the temperature from 25°C to 30°C?

2. if the temperature change is 25°C and the final temperature is 15°C what was the initial temperature?

Specific Energy Problems – with no phase change 1. How many joules of energy must be absorbed to raise the temperature of 20 g of water from

25°C to 30°C?

2. How many calories of heat are required to raise the temperature of 550 g of water from 12.0 to 18.0 ºC?

3. What mass of water (in grams) loses 200 calories of heat with a -10 °C temperature change?

If the initial temperature was 40 °C, what is the new temperature after -10 °C

Quickwrite – Explain how you could know if energy is being absorbed or released____________________________________________________________________________________________________________________________________________________15

Temperature and Thermal Energy Key Ideas7a. Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms).Thermal energy is the total energy of the particles that make up an object. Inside every object or substance are molecules or atoms. These particles are always moving. In cooler substance (ice) the particles are moving slowly. In hotter substances (water vapor) the particles move faster. At Absolute Zero (0K) all molecular motion stops. HOW KINETIC AND THERMAL ENERGY ARE RELATEDKinetic energy is a general term describing the energy associated with the motion of objects (large or small objects). Thermal energy refers to the kinetic energy of the microscopic particles (atoms and molecules) that make up all samples of matter - i.e. all objects. When you add heat to an object, you usual increase the temperature of the object and that heat increases the kinetic energy of the molecules that comprise that object. Temperature is a measure of the average kinetic energy of the internal microscopic particles.

Three temperature scales are Fahrenheit, Celsius, and KelvinFahrenheit scale – The temperature scale on which 32°F (water freezes) and 212°F (water boils).Celsius scale - The temperature scale on which 0°C (water freezes) and 100°C (water boils). Kelvin scale - The temperature scale on which zero is the temperature at which no more

energy can be removed from matter. 0 K also known as Absolute zero. Water freezes at Water boils at

1) Quantifying energy: 1 calorie = 4.18 Joules The traditional unit of energy is the calorie (cal), which is the amount of energy you need to

add to 1 gram of water to heat it by 1 C. Food is measured in units of 1000 calories called kilocalories (kcal), which is more commonly

known as the Calorie (Cal). The metric unit of energy is the joule (J). 1000 joules called kilojoules (kJ).

2) No phase change energy problemsq = m(T)Cp where: q or Q= heat energy -Q = heat lost, +Q = heat absorbed, (cal. or joules)

m = mass (g) T = TFinal – TInitial the temperature change (C)Cp = specific heat (cal/ gC or Joules/ gC)

Specific heat –is the amount of heat per unit mass (gram) required to raise the temperature by one degree Celsius. The specific heat of Water is Cp (H2O) = 1.00 cal/gC =

CgJ

Cgcal

18.400.1

The specific heat relationship only applies when there is no phase change. The specific heat relationship does not apply if a phase change is encountered, because the heat added or removed during a phase change does not change the temperature.

Example. Aluminum has a specific heat of 0.9 J/g oC. How much heat is lost when a piece of aluminum with a mass of 25 g cools from a temperature of 400.0 oC to a temperature of 30.0 oC?

First read the question and try to understand. Can you picture a piece of aluminum foil that is taken out of an oven. Imagine the aluminum losing heat to its surroundings.Explanation______________________________________________________________________________________________________________________________Specific Heat Practice Problems4

1. The temperature of a substance with a mass of 250g increases from 45oC to 65oC when the substance absorbs 5000 cal of heat. What is the specific heat capacity of the substance? 4 http://www.fordhamprep.org/gcurran/sho/sho/worksheets/worksht210a.htm. Notice pg 14 #216

2. The temperature of a substance with a mass of 150g increases from 55oC to 95oC when the substance absorbs 2000 J of heat. What is the specific heat capacity of the substance?

Material Specific Heatcal/goC J/goC

Al 0.215 0.900Cu 0.092 0.385Fe 0.107 0.448Pb 0.031 0.130Mg 0.245 1.03Zn 0.093 0.390wood 0.41 1.71sand 0.19 0.79Water (L) 1.0 4.18Air(dry)sl 0.24 1.0

3. What is the specific heat of a substance if 1800 J are required to raise the temperature of a 100 g sample by 20oC? Use the specific heat to determine the material.

4. What is the specific heat of a substance if 400 J are required to raise the temperature of a 20 g sample by 50oC? Use the specific heat to determine the material.

5. How many calories of heat are released to when the temperature of 550 g of water is reduced from 18.0 oC to 12.0 oC?

6. How much heat is lost when a 600 g piece of copper cools from 375 oC, to 25 oC?

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7. A 50 gram sample of an unknown metal cools from 58° to 18° after releasing 800 joules. What is the specific heat of the metal?

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Thermochemistry Practice #1Conversions1. How many calories are in 12.54 joules?

2. How many joules are in 100 calories?

3. 41.8 J to calories

4. Convert 1000 calories to joules.

5. How many calories are necessary to raise the temperature of 5 grams of water from 25oC to 55oC?

6. How many joules are given off when 10 grams of water cools from 40oC to 30oC?

7. How many calories are released when 25 grams of water cools from 37oC to 33oC?

8. How many joules are necessary to raise the temperature of 100 grams of water from 25oC to 28oC?

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Phase Changes Energetics7c. Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts. Identify the Processes involved and the processes whether the processes releases (exothermic) or absorbs (endothermic) energy

S

G L

Quick Write Explain what is happening to the water molecules when fogging mirrors________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Vapor pressure, equilibrium, and evaporation

Solid to liquid

Liquid to Gas

Liquid to Solid

Gas to Liquid

Phase Change Name Energetics

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a. All liquids evaporate when left out “in the air.” The highest energy molecules in the liquid phase, when they are on the surface of the liquid, escape to the gas phase.

b. Even contained liquids will evaporate, that is, they will proceed from the liquid to the gaseous state of matter.

c. However, in a contained liquid, as the liquid particles evaporate, the gas formed by them (the vapor) begins to exert a pressure just like any other gas in a container would.

d. As the pressure increases due to the growing number of gas particles, the likelihood of two gas particles interacting and re-liquefying (condensation) increases. After a while, the number of particles entering the vapor phase equals the number of particles re-entering the liquid phase. At this point, we say that a state of equilibrium has been established between the gas and liquid phases.

e. The pressure exerted by a gas that is in equilibrium with its own liquid phase at a certain temperature is called the vapor pressure of that substance.

f. Huge tables are published in huge books detailing the vapor pressures of substances. Alternatively, there are mathematical equations that can predict (or at least estimate) the vapor pressure of a liquid from some of its physical properties.

Phase Change NotesI. Phases of matter and phase changes

Energy is involved during the transition from one phase of matter to another.

You should learn how energy is involved in each of these phase transitions, and you should be able to name each of these phase transitions.

Add Energy, Energy Absorbed = EndothermicRemove Energy, Energy Released = Exothermic

(1) Melting: energy absorbed

(2) Freezing: energy released

(3) Condensation: energy released

(4) Vaporization: energy absorbed

(5) Deposition: energy released

(6) Sublimation: energy absorbed

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Phase Change Worksheet The graph was drawn from data collected as a substance was heated at a constant rate.

At point A, the beginning of observations, the substance exists in a solid state. Material in this phase

has _______________ volume and _____________ shape. With each passing minute, _____________ is

added to the substance. This causes the molecules of the substance to ____________ more rapidly which

we detect by a ________________ rise in the substance. At point B, the temperature of the substance is

______°C. The solid begins to __________. At point C, the substance is completely ____________ or in

a ___________ state. Material in this phase has _______________ volume and _____________ shape.

The energy put to the substance between minutes 5 and 9 was used to convert the substance from a

___________ to a ___________ by breaking the intermolecular bonds.

Between 9 and 13 minutes, the added energy increases the ______________ of the substance. During

the time from point D to point E, the liquid is ___________. By point E, the substance is completely in

the __________ phase. Material in this phase has _____________ volume and ___________ shape. The

energy put to the substance between minutes 13 and 18 converted the substance from a ___________ to a

___________ state. Beyond point E, the substance is still in the ______________ phase, but the

molecules are moving _______________ as indicated by the increasing temperature.

II. Heat and Phase Changesa substance that is heated will not undergo a continuous rise in temperature. Likewise, if a substance is cooled, its temperature will not decrease uniformly.

In fact, as a substance such as ice is heated, its temperature will only increase until a phase change occurs. During a phase change, the temperature of a substance does not change.

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When the temperature of a substance that is being cooled or heated does not change, it is undergoing a phase change.

Chapter 16 Energy and Chemical Change

Calorimetry – Measuring Heat Flow

Energy Added 1) Raise Temperature

2) Change Phase

Summary

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Change of state – The physical change of matter from one state to another. Melting – The change from a solid to the liquid form of

matter. Melting point – The temperature at which a substance melts. Freezing – The change from the liquid to the solid form of

matter. Freezing point – The temperature at which a substance

freezes. Vaporization - The change from the liquid to the gaseous

form of matter. Evaporation – Vaporization that occurs at the surface of a liquid. Boiling – Vaporization that occurs below the surface of a liquid. Boiling point – The temperature at which a liquid substance boils. Condensation – The change from the gaseous to the liquid form of matter. Freezing and Boiling Point Graph, Vapor Pressure and Boiling, Phase

Diagram

Energy During Change of States5

Heat of Fusion: The energy required to change a gram of a substance from the solid to the liquid state without changing its temperature is commonly called it's "heat of fusion". This energy breaks down the solid bonds, but leaves a significant amount of energy associated with the intermolecular forces of the liquid state. The equation is Q = m Hfus Q = energy, m = mass, Hfus = heat of fusion for water is 80 cal/g = 334 J/g Practice: How many calories does it take to melt 1000 gram of ice at 0 °C

Heat of Vaporization: The energy required to change a gram of a liquid into the gaseous state at the boiling point is called the "heat of vaporization". This energy breaks down the intermolecular attractive forces, and also must provide the energy necessary to expand the gas (the PV work applied). For an ideal gas, there is no longer any potential energy associated with intermolecular forces. So the internal energy is entirely in the molecular kinetic energy. The equation is Q = m Hvap where: Q = energy, m = mass and Hvap = heat of vaporization for water is 540 cal/g = 2260 J/g Practice: What is the mass of water that absorbs 10800 calories to boil at 100°C

A significant feature of the vaporization phase change of water is the large change in volume that accompanies it. A mole of water is 18 grams, and at STP that mole would occupy 22.4 liters if vaporized into a gas. If the change is from water to steam at 100°C, rather than 0°C, then by the ideal gas law that volume is increased by the ratio of the absolute temperatures, 373K/273K, to 30.6 liters. Comparing that to the volume of the liquid water, the volume expands by a factor of 30600/18 = 1700 when vaporized into steam at 100°C. This is a physical fact that firefighters know, because the 1700-fold increase in volume when water is sprayed on a fire or hot surface can be explosive and dangerous.

Calculations Involving Specific Heat and Latent Heat of Phase Change I 6

5 http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/phase2.html#c16 http://www.sciencegeek.net/Chemistry/taters/Unit7Thermochemical.htm25

Standard: Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.1. The specific heat of carbon (graphite) is 0.71 J/(g·°C). How much energy is given off as a 2 gram piece of graphite cools from 120°C to 20°C?

2. A sample of mercury has a mass of 500 grams. When it absorbs 280 joules, the temperature is found to have increased from 25°C to 29°C. What is the specific heat of mercury?

3. What is the mass of iron if it's specific heat is 0.45 J/g°C and it warms from 0°C to 40°C while absorbing 900 joules.

4. How much energy must be removed from 500 grams of water in order to cool it from 80°C to 40°C? The specific heat of water can be found on your periodic table.

5. How much energy is required to melt 4 moles of ice at its melting point? Convert mole to grams

6. How many calories are necessary to raise the temperature of 20 grams of water from 27ºC to 32ºC?

7. What is the final temperature after -8360 J are given off when 200 grams of water cools from 36ºC?

1. -142J, 2. 0.14 J/gC, 3. 50 g, 4. 2000 cal, 5. 5760 cal, 6. 100 cal.

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8. How many grams of water require 700 calories to raise the temperature of water from 40 ºC to 60 ºC?

9. How many calories are released when 150 grams of water cool from 38.5ºC to 28.5ºC?

10. How many calories are necessary to raise the temperature of 1000 grams of water from 28.4ºC to 29.4ºC?

Quickwrite Explain How can you tell if you are absorbing heat or releasing heat

______________________________________________________________________________________________________________________________________________________________________________________________________

__________________________________________________________________

Thermochemistry Practice #21. What mass of water (in grams) is needed to produce 10,000 calories of heat and a 10 oC temperature change?

2. What mass of water (in grams) is needed to produce -500 joules of heat and a -6 oC temperature change?

7. 26 deg C, 8. 35 g, 9. -1500 cal, 10. 5000 cal

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3. What mass of water (in grams) is needed to produce -100,000 calories of heat and a -10oC temperature change?

4. What mass of water (in grams) is needed to produce 20,000 calories of heat and a 2oC temperature change?

Phase Change1. How many calories does it take to melt 20g of ice at 0oC?

2. How many joules are given off when 100g of steam condenses to liquid water?

3. How many joules does it take to melt 100g of ice at 0oC?

4. How many calories are given off when 50g of water at 0oC freezes?

2. 20 g, 4. 10000 g Phase Change, 1. 1600 cal,

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5. How many joules does it take to vaporize 30g of water at 100oC and 1 atm?

6. How many calories are given off when 200g of steam condenses to liquid water?

7. How many calories does it take to vaporize 1000g of water at 100oC and 1 atm?

8. How many joules are given off when 1000g of water at 0oC freezes?

Quickwrite Explain how you know which thermo equation to use________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Using the diagram write what equations under the conditions present in each “leg” of the H2O heating/cooling curve

4. -4000 cal 6. -108000 cal 7. 540000 cal

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Quickwrite : Why the temperature is not changing during leg B_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Quickwrite: Explain how you would calculate the the amount of energy needed to convert 10 g ice at -20 C to steam at 120 C

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Calculations Involving Specific Heat and Latent Heat of Phase Change III1. How much energy is required to boil 4 moles of water at its boiling point? Convert moles to grams

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2. An engineer wants to be able to condense 10 moles of water vapor every minute. Assuming the steam is at 100°C, how much energy must be removed every minute? Convert moles to grams

3. How much energy must be absorbed by 10 grams of steam in order to raise its temperature by 100°C?

4. How much energy must be removed from 30 moles of liquid water at 0°C in order to convert it to ice?

5. A sample of ice at 0°C melts after absorbing 334 kJ of heat. How many moles of H2O are contained in the sample? Conver kJ to J to get started.

6. A sample of water at 100°C is converted to steam after absorbing 820 kJ of heat. How many moles of H2O are contained in the sample? Find mass then moles

7. How many joules of energy are needed to melt 54 grams of ice at its melting point?

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Phase Diagramsa. A particular substance can exist in several different phases – sometimes simultaneously – depending on the pressure and temperature at which the substance is held.b. The phase behavior of a substance can be summarized with a phase diagram.c. Key features:

i. Triple point: the conditions of temperature & pressure at which all three phases of matter can coexist. What is the triple point of H2O?

ii. Vapor pressure: the pressure at which a contained liquid is in equilibrium with its gas phase (vapor). 1. The boundary between the “gas” and “liquid” sections of the graph represents the vapor

pressure of the substance. As temperature goes up, the vapor pressure goes up. So, you can determine the vapor pressure for a substance at a given temperature.

iii. Normal boiling point: this is the boiling point at standard atmospheric pressure (1 atm). Notice that water can be boiled at many temperatures, depending on the pressure. In Denver, Colorado, water boils at 95°C; on Mount Everest, water boils at 70°C. What non-scientists call “boiling point” is what we call “normal boiling point”.iv. Normal freezing point: This is the freezing point at standard atmospheric pressure (1 atm). Notice that water can be turned to ice at many temperatures, depending on the pressure

d. Different substances have different phase diagrams because they behave differently as the pressure and temperature change.

Test your knowledge of phase diagrams by answering the following questions about the phase diagram for water:1. State what phase(s) of water is/are present at each of the following temperature-pressure conditions:a) at any point on curve BO________________________________________________b) at any point on curve OA_______________________________________________c) at any point on curve OC_______________________________________________d) at point O_______________________________________________e) 50 ºC and 800 mm Hg_______________________________________________2. What effect would each of the following changes have on a sample of water at any point on curve OA:a) increasing the temperature at constant pressure_______________________________________________b) decreasing the pressure at constant temperature______________________________________________

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c) decreasing the temperature at constant pressure______________________________________________d) increasing the pressure at constant temperature_______________________________________________3. Given a sample of water at any point on curve BC in the phase diagram given above, how could more liquid water in the sample be converted into a solid?

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Practice Questions1. The specific heat of copper is about 0.4 joules/ gramºC. How much heat is needed to change the temperature of a 30-gram sample of copper from 20.0 ºC to 60.0 ºC?

A 1000 J B 720 JC 480 JD 240 J2. Examine the graph of the temperature of a compound versus heat added to the compound. Which of the following most likely happens as the compound is heated from point x to point y?A The phase of the compound changes.B The mass of the compound is increasing. C The molecules of the compound lose potential energy.D The molecules of the compound are breaking apart into atoms.

3. To determine if a reaction is exothermic, a student should use a —A pH probe B motion sensor C pressure sensor D temperature probe

4. As heat is added to a substance undergoing a phase change, the temperature remains constant because the energy is being used to —A break covalent bonds B lower the specific heat capacityC overcome intermolecular forces D oppose electron cloud repulsions

5. What happens when energy is removed from liquid water?A Molecules slow down, and more hydrogen bonds are formed.B Molecules slow down, and more hydrogen bonds are broken.C Molecules move faster, and more hydrogen bonds are formed.D Molecules move faster, and more hydrogen bonds are broken.

6. Consider this phase diagram: At what temperature does the normal boiling point occur? Explain.

7. The gases helium, neon, and argon are in separate containers at 55°C. Which is true about the kinetic energy of the gases?A Helium has the lowest mass and therefore greatest kinetic energy.B They each have a different kinetic energy.C Argon has the greatest mass and therefore the greatest kinetic energy.D They all have the same average kinetic energy.

8. An open container of water is brought to a boil and heated until all of the water is converted to water vapor.Which describes the changes in the water molecules?A The molecules speed up and move farther apart.B The molecules speed up and move closer together.

C The molecules slow down and move farther apart.D The molecules slow down and move closer together.

9. A student has a beaker containing 55 g of water at 100°C. How much heat is needed to convert the water to steam? A 120,000 J B 18,000 J C 2,200 J D 330 J

10. How many grams of ice will melt at 0°C if the ice absorbs 420. J of energy?A 0.186 g B 0.795 g C 1.26 g D 5.38 × 104 g

11. Between points X and Y, which would be observed?A Solid and liquid will be present.B Only vapor will be present.C Liquid and vapor will be present.

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D Only liquid will be present.

12.What process is occurring when a substance changes from point X (-130°C, 50 kPa) to point Y (30°C, 100 kPa)?A boilingB freezing

C meltingD sublimation

Phase Diagram for Water

Identify the line segments Phase Change Energetics__________________ Phase change from solid to liquid ____________ ______ ___________________ Phase change from liquid to solid ____________ __________________________ Phase change from liquid to gas ____________ __________________________ Phase change from gas to liquid ____________ __________________________ Phase change from solid to gas ____________ __________________________ Phase change from gas to solid ____________ __________________________ Point where all three phases exist at the same time in equilibrium Provide the name for these occurrences

____________________ Temperature at which a substance melts at 1 atm pressure ____________________ Temperature (Tc) above which substances cannot exist as solids

____________________ Temperature at which a substance melts at 1 atm pressure

ENERGY DIAGRAM PRACTICE Heat of reaction is the amount of heat that must be added or removed during a chemical reaction in order to keep all of the substances present at the same temperature. If the pressure in the vessel containing the reacting system is kept at a constant value, the measured heat of reaction also represents the change in the thermodynamic quantity called enthalpy, or heat content, accompanying the process—i.e., the difference between the enthalpy of the substances present at the end of the reaction and the enthalpy of the substances present at the start of the reaction.

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Thus, the heat of reaction determined at constant pressure is also designated the enthalpy of reaction, represented by the symbol ΔH. If the heat of reaction is positive, the reaction is said to be endothermic; if negative, exothermic.The prediction and measurement of the heat effects that accompany chemical changes are important to the understanding and use of chemical reactions. If the vessel containing the reacting system is so insulated that no heat flows into or out of the system (adiabatic condition), the heat effect that accompanies the transformation may be manifested by an increase or a decrease in temperature, as the case may be, of the substances present. The ∆H of a reaction is the difference between the enthalpy (Heat content) of the reactants and products. ∆H = Hfinal – Hintial

Some reactions are reversible, that is there is a forward reaction like we usually have: Reactants →ProductsAND for a backward reaction there can be the opposite reaction: Products →Reactants.A reversible reaction is written as: Reactants Products

Practice Questions1. The heat content of the reactants of the forward reaction is about ____________kilojoules.2. The heat content of the products of the forward reaction is about ____________ kilojoules.3. The heat content of the activated complex of the forward reaction is about ____________kilojoules.4. The activation energy of the forward reaction is about ____________ kilojoules.5. The heat of reaction (∆H) of the forward reaction is about ____________ kilojoules.6. The forward reaction is _______________________ (endothermic or exothermic).7. The heat content of the reactants of the reverse reaction is about ____________kilojoules.8. The heat content of the products of the reverse reaction is about ____________ kilojoules.9. The heat content of the activated complex of the reverse reaction is about ____________ kilojoules.10. The activation energy of the reverse reaction is about ____________ kilojoules.11. The heat of reaction (∆H) of the reverse reaction is about ____________kilojoules.12. The reverse reaction is ________________________ (endothermic or exothermic).

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Practice1. Does the graph represent an endothermic or exothermic reaction?

2. Determine the heat of reaction, ∆H, for this reaction.

3. Determine the activation energy, Ea, for this reaction.

4. What is the energy of the activated complex for this reaction?

5. Determine the reverse activation energy, Ea, for this reaction

6. Is this an endothermic or exothermic reaction? 7. Determine the heat of reaction, ∆H, for this reaction. 8. Determine the activation energy, Ea for this reaction.

9. What is the energy of the activated complex for this reaction?

10. Determine the reverse activation energy, Ea for this reaction.

Identify the type of reactions that each graph depicts

____________________________________________________________

A=

B=

C=

D=

∆H=

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Reaction Rate Calculations using Mole Ratios1. In the following decomposition reaction, 2 N2O5 → 4 NO2 + O2

oxygen gas is produced at the average rate of 9.1 × 10-4 mol · L-1· s-1. Over the same period, what is the average rate of the following: the production of nitrogen dioxide and the loss of nitrogen pentoxide

From the equation we see that for every 1 mole of oxygen formed, four moles of nitrogen dioxide are produced.

Thus, the rate of production of nitrogen dioxide is four times that of oxygen:rate NO2 production = 4mol NO2 × 9.1 × 10-4 mol · L-1· s-1 = 3.6 × 10-3 mol NO2 · L-1· s-1

1mole O2

Nitrogen pentoxide is consumed at twice the rate that oxygen is produced:(neg rate) rate loss of N2O5 = 2 mole N2O5 × (9.1 × 10-4 mol · L-1· s-1) = 1.8 × 10-3 mol N2O5· L-1· s-1

1mole O2

2. Consider the following reaction: N2(g) + 3 H2(g) → 2 NH3(g) If the rate of loss of nitrogen gas is 0.03 mol · L-1· s-1

What is the rate of production of ammonia?

What is the rate of consumption of hydrogen gas?

3. Consider the reaction: C2H4 (g) + 3O2(g) 2CO2(g) + 2H2O(g)

At certain conditions 0.26 moles of C2H4 is consumed in 3.0 minutes.What is the rate of consumption of C2H4 in g/s ?

4. Consider the reaction: C2H5OH (l) + 3O2(g) → 2CO2(g) + 3H2O(g)At certain conditions 11.2 L of CO2 is produced in 180.0 sec at STP. What is the rate of consumption of C2H5OH in g/min ? Hint convert L to moles and then to grams

5. If the below reaction takes place inside a sealed reaction chamber, then which of these procedures will cause a decrease in the rate of the reaction? 2CO + O2 → 2CO2a. Raising the temperature of the reaction chamber c. Removing the CO2 as it is formedb. Increasing the volume inside the reaction chamber d. adding more CO to the reaction chamber.

6. A chemist wishes to determine the rate of reaction of zinc with hydrochloric acid. The equation for the reaction is:

Zn(s) + 2HCl(aq) → H2(g) + ZnCl2(aq)a) What will happen to the [H+] as the reaction proceeds? _________________________ b) What will happen to the [H2] as the reaction proceeds? _________________________

Lock and Key Model of Enzymatic Interactions with Substrates

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KINETICS Three things are required for a reaction to occur: SUCCESSFUL COLLISON1. Molecules must collide.2. They must collide with enough energy to break old bonds so new ones can form.3. They must collide in the correct orientation.Reaction Rates Definition of RATE: change in concentration over change in time∆Concentration = ∆Reactants = ∆Products ∆ Time ∆ Time ∆ Time

Example: H2 + Cl2 → 2HClTime Seconds [H2] [Cl2] [HCl]0 0.03 0.05 0.04 0.02 0.04 0.02

∆Reactants ∆Products ∆ Time

Factors that Affect RATE: temp= increasing temp increases both the frequency and energy of collisions, so rate

increases. More collisions at higher energy so chance of exceeding the activation energy increase.

concentration: increasing [ ] of reactants means more collisions per unit time only. The rate of a reaction is directly proportional to concentration. As the compounds react, the concentration decreases and the rate slows.

pressure (gases only): greater the pressure the more “concentrated” the gas, so the faster the rate . Increasing pressure occurs by increasing temperature or decreasing volume.

surface area (solids): the greater the surface area the faster the rate. Ex powdered NaHCO3 with vinegar produced CO2 faster than chunky NaHCO3

catalyst: increases both forward and reverse reaction rates because it lowers forward and reverse activation energy. Biochemical catalysts are called enzymes. Enzymes are proteins that are not used up in the reactions. Catalysts are reused. Inhibitors do the opposite. Inhibitors are important for biological regulation.

nature of reactants: phase=aqueous faster than gas faster than liquid faster than solid because water has already “broken bonds” dissociated ions so they are free to recombine. Strength and # of bonds: the more bonds to be broken the slower the rate. The stronger the bonds the slower the rate

Stirring – increases the frequency of collisisons. Reaction mechanism: the more steps, the slower rateReaction Mechanisms: “behind the scene” steps to a reaction. a) slow step= rate-determining step. THIS can be ANY numbered step.b) You are only as strong as your weakest link so changing the [ ] of a substance NOT in the rate-determining step will NOT affect ratec) To get the NET equation, cross out “identicals” (otherwise known as intermediates), add like substances on the same side, cross out substances on different sides leaving “leftovers” on the greater side Ex. Step #1: O3 → O2 + O fast Step #2: O + O3 → 2O2 slow Net= 2 O3 → 3 O2 Intermediate = O Rate-determining step = #2REACTION RATES TEXTBOOK CHAPTER 17VOCABULARY:

1. Reaction rate__________________________________________________________2. Collision theory_________________________________________________________3. Activated complex_______________________________________________________

Calculate the rate of HCl production

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4. Transition state________________________________________________________5. Activation Energy_______________________________________________________6. Catalyst______________________________________________________________7. Inhibitor______________________________________________________________

Questions1. What does the reaction rate indicate about a particular chemical reaction?

2. How is the rate of a chemical reaction usually expressed?

3. In a typical reaction, as time passes, the amount of __________ decreases and the amount of ___________ increases.

3. How would you express the rate of a chemical reaction A B based on the concentration of reactant A? How would that rate compare with the reaction rate based on the product B?

4. What is the collision theory and how does it relate to reaction rates?

5. According to the collision theory, what must happen in order for two molecules to react?

6. How is the speed of a chemical reaction related to the spontaneity of the reaction?

7. What does the activation energy for a chemical reaction represent?

8. What is the role of the activated complex in a chemical reaction?9. Suppose two molecules that can react collide. Under what circumstances do the

colliding molecules not react?

10. How is the activation energy for a chemical reaction related to whether or not a collision between molecules initiates a reaction?

11. In the activated complex for a chemical reaction, what bonds are broken and what bonds are formed?

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12. If A B is exothermic, how does the activation energy for the forward reaction compare with the activation energy for the reverse reaction (B A)?

Factors Affecting Reaction RatesFactor Effect on reaction rate and why

Practice1. The minimum energy required for an effective collision is called(A) energy of enthalpy. (C) free energy.(B) activation energy. (D) kinetic energy

2. In Biochemistry, catalysts are called and made of:(A) Polymers, fatty acids (B) enzymes, proteins (C) carbohydrates, amino acids (D) enzymes, fats

3. An increase in temperature generally has what impact on the rate of a reaction?(A) It will increase. (C) There is no way to measure the change.(B) It will stay the same. (D) It will decrease. 4 To be effective, a collision requires(A) sufficient energy. (C) a favorable orientation.(B) sufficient energy and a favorable orientation. (D) a reaction mechanism.

5. Which expression represents a reaction rate?(A) time/mass (B) concentration/time (C) energy/time (D) time/energy

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6. What happens to a catalyst in a reaction?a. It is unchanged. c. It is incorporated into the reactants.b. It is incorporated into the products. d. It evaporates away.

7. Which of the following changes will cause an increase in the rate of the below reaction?C6H6 + Br2 C6H5Br + HBra. increasing the concentration of Br2 c. increasing the concentration of HBrb. decreasing the concentration of C6H6 d. decreasing the temperature

8.If the below reaction takes place inside a sealed reaction chamber, then which of these procedures will cause a decrease in the rate of the reaction? 2CO (g) + O2(g) →2CO2 (g)a. Raising the temperature of the reaction chamber c. Removing the CO2 as it is formedb. Increasing the volume inside the reaction chamber d. adding more CO to the reaction.

9. The rate equation for a chemical reaction is determined by(A) theoretical calculations.(B) measuring reaction rate as a function of concentration of reacting species.(C) determining the equilibrium constant for the reaction.(D) measuring reaction rates as a function of temperature

10. Which line in the diagram represents the activation energy for a forward reaction? (A) A (B) B (C) C (D) D

11. The addition of a catalyst in a chemical reaction(A) increases the concentration of products at equilibrium.(B) increases the fraction of reactant molecules with a given

kinetic energy.(C) provides an alternate path with a different activation energy.(D) lowers the energy change in the overall reaction.

Catalytic Converters – Improving our Air Quality

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This balanced equation represents a chemical reaction using palladium, Pd, as a catalyst. (Pd)

CO2 (g) + H2O (l) → H2CO3(l)Without palladium the reaction is slow and produces low concentrations of product. How does the palladium increase the speed of the reaction?a. The palladium reacts with the water b. The palladium lowers the activation energyc. The palladium purifies the carbon dioxided. The palladium increases the reaction temperature

Equilibrium Vocabulary Interaction1. What is the definition of equilibrium ____________________________________________________________________________________________________________________________________________________________________________________________________

2. What is a reversible reaction_____________________________________________________________________________________________

_____________________________________________________________________________________________

_____________________________________________________________________________________________

3. After balancing and checking with an inventory write the forward and the reverse reaction for the following equation:

N2 (g) + H2 (g) NH3 (g)

Forward Reaction

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Reverse Reaction

4. What states of matter should be included in an equilibrium expressions

______________________________________________________________________________________

5. What states of matter should not be included in equilibrium expressions

______________________________________________________________________________________

6. Write the equilibrium expression for the reaction: oxygen gas + hydrogen gas to form water vapor. Don’t forget to balance equation before writing the equilibrium expression.

7. When given the following quantitative values for Keq mean which is favored?a) Keq = 0.4 b) Keq = 12 c) Keq= 1.2 d) Keq = 10-2

Equilibrium Notes 1. Equilibrium Definition: Rate of forward reaction = Rate of reverse reaction2. Writing Keq’s: Because the concentrations of substances in a system at chemical equilibrium

are constant over time, chemical expressions related to each concentration will also be constant. Here is a general equation for a reaction at equilibrium: aA + bB c C + d D

The general expression for the equilibrium constant of a chemical reaction is ba

dc

BADCKeq

a) products in NUMERATOR, use [ ] around substances and include their phases reactants in DENOMINATORb) (+) signs separating substances in equation BECOME (x) multiplication signsc) coefficients BECOME exponentsd) NO liquids or solids !!!!!! Only aqueous and gas

3. Solving for Keq’s: put the ENTIRE numerator in ( ) and the ENTIRE denominator in ( )4. Interpreting the equilibrium constant

If the Keq= >>1 then PRODUCTS are favored More products than reactants at equilibrium.If Keq near one= significant amounts of both reactants and productsIf Keq= <<1 the reactants favored More reactants than products at equilibrium.

Equilibrium Expression Summary

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Equilibrium Expression Summary

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Le Chatelier’s Principle If a stress is applied to a system at equilibrium, the system shifts in the direction

that relieves the stress. A stress is any kind of change in a system at equilibrium that upsets the equilibrium

o Changes in concentrationo Changes in volume (or pressure) – decreasing volume of reaction vessel at

constant temperature increases the pressure inside. Just for gaseso Changes in temperature. Shifts the equilibrium and the value of Keq

Changes in Concentration: When a reactant is added to a system at equilibrium, the reaction shifts in the

direction of the formation of products. When a reactant is removed, the reaction shifts in the direction of formation of

reactants. Adding a product to a reaction at equilibrium pushes a reversible reaction in the

direction of reactants. Removing a product always pushes a reversible reaction in the direction of the

products.

Changes in Temperature Increasing the temperature causes the equilibrium position of a reaction to shift in

the direction that absorbs heat. Heat can be considered as reactant or product. If temp increases shift AWAY from heat If temp decreases shift TOWARD heat

Changes in Pressure A change in the pressure on a system affects only gaseous equilibria that have

unequal number of moles of reactants and products. Equal number of moles of gas on each side = no change.

Increasing pressure will shift the reaction in the direction that produces fewer numbers of gaseous molecules.

If pressure increase shift to side with LESS moles of gases If pressure decreases, shift to side with GREATER moles of gases

Count the moles to decide which way to apply the stress

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As the temperature increases, the equilibrium constant decreases as the yield of ammonia decreasesTemperature

(oC) Keq

25 6.4 x 102

200 4.4 x 10-1

300 4.3 x 10-3

400 1.6 x 10-4

500 1.5 x 10-5

AMMONIA PRODUCTION CASE STUDY7

The Haber process is the production of ammonia from a reaction between nitrogen and hydrogen, because of an iron substitute. This process is known for the commercial synthesis of ammonia. There is great abundance of nitrogen in the air when it is combined with hydrogen under extreme pressure and high temperature. This process is a great example of chemical equilibrium.The Haber process, also known as the Haber-Bosch Process, was founded by Fritz Haber and Carl Bosch, both who were German Chemists. Haber discovered the conditions for the formation of ammonia, and Bosch discovered the work of high-pressure on chemical reactions (developed into industrial process). Both were awarded the Nobel Prize. During the 1920’s, there was a shortage of the world's supply for fixed nitrogen. Nitrogen was mainly used for fertilizer. Fertilizer was used in order to produce food, so that in WWI people could continue to fight. It only requires 1 percent of the world's energy to make 500 million tons of artificial fertilizer per year, which, in turn, helps feed 40 percent of the world's population. What no one could have imagined at that time is that much of the extra fertilizer added ends up in waterways and eventually the ocean negatively affecting aquatic ecosystems - Eutrophication. THE PROCESSThe Haber process takes nitrogen gas from air and combines it with molecular hydrogen gas to form ammonia gas. This is an exothermic reaction, meaning it releases energy so that the sum of the enthalpies of N2 and H2 (the reactants) is greater than the enthalpy of NH3 (the products).

N2(g) + 3H2(g) → 2NH3(g) ΔH=-92.4 kJ

which is a reversible reaction:

2NH3(g) → N2(g) + 3H2(g) ΔH=+ 92.4 kJ mol-1

Le Châtelier's Principle8

increasing the pressure causes the equilibrium position to move to the right resulting in a higher yield of ammonia since there are more gas molecules on the left hand side of the equation (4 in total) than there are on the right hand side of the equation (2). Increasing the pressure means the system adjusts to reduce the effect of the change, that is, to reduce the pressure by having fewer gas molecules.

decreasing the temperature causes the equilibrium position to move to the right resulting in a higher yield of ammonia since the reaction is exothermic (releases heat). Reducing the temperature means the system will adjust to minimize the effect of the change, that is, it will produce more heat since energy is a product of the reaction, and will therefore produce more ammonia gas as well. However, the rate of the reaction at lower temperatures is extremely slow, so a higher temperature must be used to speed up the reaction which results in a lower yield of ammonia.

Rate considerations: A catalyst such as an iron catalyst is used to speed up the reaction

by lowering the activation so that the N2 bonds and H2 bonds can be more readily broken.

Increased temperature means more reactant molecules have sufficient energy to overcome the energy barrier to reacting (activation energy) so the reaction is faster at higher temperatures (but the yield of ammonia is lower as discussed above). A temperature range of 400-500oC is a compromise designed to achieve an acceptable yield of ammonia (10-20%) within an acceptable time period.

During industrial production of ammonia, the reaction never reaches equilibrium as the gas mixture leaving the reactor is cooled to liquefy and remove the ammonia. The remaining mixture

7 http://chemwiki.ucdavis.edu/Physical_Chemistry/Chemical_Equilibrium/Case_Studies/Haber_Process. Adapted M.Elizabeth3/23/148 http://www.ausetute.com.au/haberpro.html

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Keq =[NH3]2

[N2][H2]3

of reactant gases are recycled through the reactor. The heat released by the reaction is removed and used to heat the incoming gas mixture

What are the conditions that the industrialists have found to maximize ammonia production.

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Ammonia Gas Production EquilibriumN2(g)+ 3H2(g) 2NH3(g)

Not equal concentration totals, but the number of NH3 decomposition is equal to the number of NH3 creation.

Opposing processes are in equilibrium:Forward rate (right) equals backwards rate (left)

Factor which affects only heterogeneous reactions (more than one phase)Surface area -when 2 different phases react, reaction can only take place on surface.

-

increase surface area by cutting solid into smaller pieces (liquids in smaller droplets)

- In general - reactants with solids

are slow (except powdered)- gaseous reactants are faster (but watch for diatomic bonds!)- reactants in ionic solution. are fastest if no bonds to breakExample: Precipitation reaction Ag+(aq) + Cl-(aq) AgCl (s)

(aqueous ions are mobile (unlike in a solid ) and more concentrated than molecules in a gas)Equilibrium Practice Problems IMemorize49

(g)(l)(s)(aq)

1. For the reaction balance firs: SiH4(g) + O2(g) SiO2(g) + H2O(g)a. Write the equilibrium equation in the forward reaction:

b. What is the equilibrium constant if [SiH4] = 0.45M; [O2] = 0.25M; [SiO2] = 0.15M; and [H2O] = 0.10M at equilibrium?

c. Which is favored reactants or products? Explain how you know

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d. If the reaction is not yet at equilibrium and you need to find out which direction it is headed calculate a temporary equilibrium constant called a reaction quotient using the following concentrations [SiH4] = 0.34M; [O2] = 0.22M; [SiO2] = 0.35M; and [H2O] = 0.20M. Compare the reaction quotient with the equilibrium constant you calculated earlier. Which direction would the reaction go? (Towards products or reactants?)

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CHEMICAL EQUILIBRIUMReversible reaction - one that can occur in both the forward and the reverse direction

Example: N2 (g) + 3H2 (g) 2NH3 (g)2NH3 (g) N2 (g) + 3H2 (g)N2 (g) + 3H2 (g) 2NH3 (g)

Chemical equilibrium - state in which the forward and the reverse reactions balance each other because they take place at equal rates.

Equilibrium Expressions and Constants

Law of equilibrium – at a given temperature, a chemical system may reach a state in which a particular ratio of reactant and product concentrations has a constant value.

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Example: aA + bB cC + dDKeq = C c D d This is the equilibrium constant expression.

AaBb

Equilibrium constant, Keq, is the numerical value of the ratio of product concentrations to reactant concentrations.

Keq 1 More products than reactants at equilibriumKeq < 1 More reactants than products at equilibrium

To write equilibrium expressions: if the product or reactant is a solid or liquid, they are omitted in the expression because their concentration is constant at a given temperature.

Examples: a) H2 (g) + I2 (g) 2HI(g) b)C2H5OH(l) C2H5OH(g) c)I2 (g) I2 (s)

Keq = Keq = Keq =

d)2H2 (g) + O2 (g) 2H2O(g) e)2H2 (g) + O2 (g) 2H2O(l) f)2NH3(g) N2(g)+ 3H2(g)

Keq = Keq = Keq =

Determining the value of equilibrium constants: just plug-in the concentrations to the equilibrium constant expression.

Sample Problem: Calculate the value of Keq for the formation of ammonia given the concentration data once equilibrium has been established.N2 (g) + 3H2 (g) 2NH3 (g) NH3 = 0.9 mol/L N2 = 0.5 mol/L

H2 = 1.7 mol/L

Practice: Write Keq expressions for the following reactions II.

1 2N2H4 (g) + 2NO2 (g) 3N2 (g) + 4H2O (g)

2 2NbCl4 (g) NbCl3 (g) + NbCl5 (g)

3 I2 (g) 2I(g)

4 2SO3 (g) 2SO2 (g) + O2 (g)

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5 2NaHCO3 (s) Na2CO3 (s) + H2O (g) + CO2 (g)

6 C6H6 (l) C6H6 (g)

7 Fe3O4 (s) 4H2 (g) 3Fe(s) + 4H2O (g)

8. HCN (aq) + H2O (l) H3O+(aq) + CN- (aq)

9 2NO(g) + H2 (g) N2 (g) + H2O (g)

10. Ag+(aq) + NH3 (g) Ag(NH3)2+ (aq)

11 4NH3 (g) + 5O2 (g) 4NO2 (g) + 6H2O (g)

12 CoCl2 (g) CO (g) + Cl2 (g)

Equilibrium Practice Problems 3

1. For the reaction predict which way the reaction will shift: left, right, or none and why: 2A(g) + B(s) ↔ C(g)

a. the concentration of B is increased ________________________________________ b. the amount of C is decreased ____________________________________________c. the amount of A is decreased ____________________________________________d. the pressure is increased________________________________________________

2. For the reaction below, what would speed up the reaction? NH4+ (aq) + H2O (l) ↔ NH3(g) + H3O+(aq)

a. the forward reaction b. the reverse reaction

c. the concentration of NH4+ is increased _____________________________________ d. the amount of H3O+ is decreased __________________________________________

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e. the amount of NH3 is decreased __________________________________________f. the pressure is increased________________________________________________

3. An equilibrium shift to the right means: a. more products are produced b. more reactants are produced c. nothing happens

4. Use this reaction for each of the following: 2NO2 (g) + O2 (g) ↔ 2NO3 (g)

a. Write the expression for the equilibrium constant.

b. If gas concentrations are as follows, 2.00 M NO2, 1.75 M O2, and 1.00 M NO3, calculate Keq

c. Using Keq from part b, are the reactants or products favored and why?

Equilibrium Practice 41. For the reaction: SiH4(g) + O2(g) SiO2(g) + H2O(g)

a. Write the equilibrium equation in the forward reaction:

b. What is the equilibrium constant if [SiH4] = 0.45M; [O2] = 0.25M; [SiO2] = 0.15M; and [H2O] = 0.10M at equilibrium?

2 For the reaction: H2 (g) + I2 (g) 2HI (g)

a) At equilibrium in a particular experiment, the concentrations of H2, I2, and HI were 0.15 M,0.033 M, and 0.55 M, respectively. what is the equilibrium expression and constant for these conditions?

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b) If there were 8. moles of H2 and 8 moles of I2 in a 500.0 mL container at equilibrium, how many moles of HI would be present?

3. The equilibrium constant is 0.190 at 73oC for the decomposition of COBr2 : COBr2 CO + Br2 (all gases)

If the concentrations of both CO and Br2 are 0.402M, and the concentration of COBr2 is 0.950M, is the system at equilibrium? If not, which way does it proceed?

http://www.chem1.com/acad/webtext/chemeq/Eq-01.htm modiefied 2/16l/12 ME

EQUILIBRIUM CONSTANT (Keq)Identify whether a reaction is homogeneous or heterogeneous. Write the expression for the equilibrium constant Keq for the reactions below. Using the equilibrium constant expressions you determined, calculate the value of Keq under the given conditions. Remember for heterogeneous reactions, the concentration terms for pure solids and pure liquids are not included in the expression for equilibrium constant. The concentration of pure solids and liquids remain constant, and these terms are merged into the equilibrium constant or by convention their concentrations are taken as unity, i.e., [solid] = 1, [liquid] = 1, therefore having no effect on the value of the equilibrium constant.

1. N2(g) + 3 H2(g) 2NH3(g) [NH3] = 0.0100 M, [N2] = 0.0200 M, [H2] = 0.0200 M

2. KCLO3(s) 2KCL(s) + 3 O2(g) [O2] = 0.0500 M

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3. H2O(l) H+(aq) + OH-(aq) [H+] = 1x10-8 M, [OH-] = 1x10-6 M

4. 2CO(g) + O2(g) 2 CO2(g) [CO] = 2.0 M, [O2] = 1.5 M, [CO2] = 3.0 M

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5. Li2CO3(s) 2Li+(aq) + CO3-2(aq) [Li+] = 0.2 M, [CO3

-2] = 0.1 M

Stress Reduction and Vocabulary1. Consider the following equilibrium equation: CH3OH (g) + 101 kJ CO (g) + 2 H2 (g)

a. Increasing the concentration of CO will

b. Increasing the pressure of the system will

c. Increasing the volume of the container for the reaction will

d. Placing the reaction vessel in a water bath to remove heat from the reaction will

e. Removing the hydrogen gas through a secondary reaction will

f. Adding a catalyst will

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2. Will raising the temperature of an equilibrium system favor exothermic reactions, endothermic reactions, or all reactions? Explain!

3. How do you know a reaction has reached equilibrium? Discuss the rates of the forward and reverse reactions as well as the concentration of reactants and products in your answer._____________________________________________________________________________________

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LE CHATELIER’S PRINCIPLE Practice 1Complete the following chart by writing left towards products, right towards reactants, or none for the equilibrium shift, and decreases, increases, or remains the same for the concentrations of reactants and products, and for the value of K.

N2 (g) + 3H2 (g) 2NH3 (g) + 22.0 kcal

Stress Equilibriumshift N2 H2 NH3 K

1. Add N2

2. Add H2

3. Add NH3

4. Remove H2

5. Remove N2

6. Remove NH3

7. Increase

temperature

8. Decrease

temperature

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9. Increase

pressure

10. Decrease

pressure

What caused a change in the equilibrium constant and why

Le Chatelier’s Principle states that when a system at equilibrium is subjected to stress, the system will shift its equilibrium point in order to relieve the stress.

Concentration

Pressure

Temperature

NaOH(aq) Na+(aq) + OH-(aq) + 10.6 kcal(Remember that pure solids and liquids do not affect equilibrium values)

Stress Equilibriumshift NaOH Na+ OH- K

1. Add NaOH

2. Add NaCl (Adds Na)3. Add KOH (Adds OH-)4. Add H+

(Removes OH-)5. Increase temperature

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6. Decrease temperature7. Increase pressure8. Decrease pressure

Le Chatelier’s Principle Practice II _________________________

How is the equilibrium position of these reactions affected by the given changes? Indicate the change by the arrow pointing on the direction the equilibrium would shift to.

1. PCl5 (g) + heat PCl3 (g) + Cl2 (g)

a. addition of Cl2 c. removal of heat

b. increase in pressure d. removal of PCl3 as it is formed

2. C(s) + H2O(g) CO(g) + H2 (g) + heata. lowering the temperature c. removing hydrogen

b. increasing the pressure d. adding water vapor

3. N2 (g) + 3H2 (g) 2NH3 (g) + energy a. removing hydrogen d. adding ammonia

b. adding nitrogen e. cooling the system

c. decreasing pressure f. increasing volume

4. C2H2 (g) + H2O(g) CH3CHO(g) + 151 kJa. increase CH3CHO d. decrease C2H2

b. increase H2O e. decrease temperature

c. increase pressure f. decrease CH3CHO

How would decreasing the volume of the reaction vessel affect each of these equilibria?

5. 2SO2 (g) + O2 (g) 2SO3 (g)

6. H2 (g) + Cl2 (g) 2HCl(g)

7. 2NOBr(g) 2NO(g) + Br2 (g)

8. CO(g) + Cl2 (g) CO2 (g) + 3FeO(s)

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Predict how this equilibrium would respond to simultaneous increase in both temperature and pressure.

9. CO(g) + Cl2 (g) CoCl2 (g) ΔH = -220 kJTemperature pressure overall

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Equilibrium Practice Test

1. If the temperature of the equilibrium system CH3OH(g) + 101 kJ CO(g) + 2H2(g) increases,a. [CH3OH] increases and [CO] decreases.b. [CH3OH] decreases and [CO] increases.c. [CH3OH] increases and [CO] increases.

d. the concentrations in the system do not change.

2. If the pressure on the equilibrium system N2(g) + 3H2(g) 2NH3(g) is increased,a. the quantity of N2(g) increases.b. the quantity of NH3(g) decreases.c. the quantity of NH3(g) increases.

d. the quantities in the system do not change.

3. If the system N2(g) + 3H2(g) 2NH3(g) has come to equilibrium and then more N2(g) is added,a. [H2] increases and [NH3] increases. c. [H2] decreases and [NH3] increases. b. [H2] decreases and [NH3] decreases. d. both [H2] and [NH3] remain the same.

4. Pressure only has an effect on reactions taking place in aa. gas. b. liquid. c. solid. d. closed container.

5. Which of the changes listed below would shift the following reaction to the right?4HCl(g) + O2(g) 2Cl2(g) + 2H2O(g)a. addition of Cl2 c. increase of pressureb. removal of O d. decrease of pressure

6. At equilibrium,a. the forward reaction rate is lower than the reverse reaction rate.b. the forward reaction rate is higher than the reverse reaction rate.c. the forward reaction rate is equal to the reverse reaction rate.d. no reactions take place.

7. In the equation W + X Y +Z , what represents the concentrations of the products?a. [Y] and [Z] c. [W] and [Y]b. [W] and [X] d. [X] and [Z]

8. What is the expression for the equilibrium constant for the reaction described by the following equation? 2SO2(g) + (O2)(g) 2SO3(g)

9. What is the equilibrium constant expression for the following reaction?Fe(OH)3(s) Fe3+(aq) + 3OH- (aq)

10. If the system 2CO(g) + O2(g) 2CO2(g) has come to equilibrium and then more CO2(g) is added,a. [CO] increases and [O2] decreases. c. both [CO] and [O2] increase.b. [CO] decreases and [O2] increases. d. both [CO] and [O] decrease.

11. If the pressure on the reaction N2(g) + O2(g) 2NO(g) at equilibrium is increased,a. the quantity of N2(g) increses.b. the quantity of NO(g) increases.61

c. the quantity of NO(g) decreases.d. the quantities in the system do not change.

12. If the temperature of the equilibrium system X + Y XY + 25 kJ decreases,a. [X] decreases and [XY] increases.b. [X] increases and [XY] decreases.c. [X] decreases and [XY] decreases.d. the concentrations of reactants and products do not change.

13. A very high value of the equilibrium constant for a reaction indicates thata. equilibrium is reached slowly. c. reactants are favored.b. products are favored. d. equilibrium has been reached.

14. Consider the reaction N2 (g) +3H2 (g) 2NH3 (g). What is the effect of decreasing the volume on the contained gases?a. The reaction shifts toward the product gas.b. The system reacts by increasing the number of gas molecules.c. The pressure on the gases decreases momentarily.d. Ammonia is consumed in the reaction.

15. The K of a reaction is 4 x 10-2 . At equilibrium, the ____.a. reactants are favoredb. products are favoredc. reactants and products are present in equal amountsd. rate of the forward reaction is much greater than the rate of the reverse reaction

16. A very low value of the equilibrium constant for a reaction indicates thata. equilibrium is reached slowly. c. reactants are favored.b. products are favored. d. equilibrium has been reached.

Explain What is included in equilibrium expression and what is not included____________________________________________________________________________________________________________________________________________________Explain how to interprete Keq values in terms of the amounts of reactants and products____________________________________________________________________________________________________________________________________________________

Le Châtlier’s Principle PRACTICE SUMMARY

Explain how the following changes in reaction conditions will affect the position of the equilibrium below, and explain your reasoning. A(g) + B(aq) C(s) ΔHrxn= -453 kJ/mol

1) The pressure of A in the reaction chamber is increased.

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2) The temperature of the reaction is increased by 200°C.

3) A catalyst is added to the system.

4) As the reaction progresses, more of compound B is steadily added to the reaction chamber.

5) An inhibitor is added to the reaction chamber.

6) Argon gas is added to the reaction chamber, doubling the pressure.

Note Taking Guide: Episode 1301 CHEMISTRY: A Study of MatterTemperature:• a measure of the _____________ ____________ energy of the particles in a sample of matter• does not depend on the amount of ______________ in the sample• symbol is _________; unit is _________Heat: ____________ amount of ______________ energy that flows because of a difference in _________________.• depends on _____________ of sample• symbol is _________ ; unit is _____________ (1 cal = 4.18 _____ )

Specific heat capacity:• amount of ______ required to raise the ______________ of 1 ____ of substance 1 ______

Kinetic energy is _____________________________________Potential energy is ___________________________________Potential energy is hiding and cannot be ___________________.Only _____________ in P.E. can be measured.

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• symbol is ________ ; unit is ________

When heat (Q) is absorbed by a system, part of it (Cp) goes into storage as _____________ energy and part of it is used to make the molecules move around __________ , raising the ___________________ (Δt).Why does sand get hotter in the day and colder at night than the water?

Heating Curve for WaterI: Heat is being used to raise the ____________ of the _______. Q = ____ X ____ X ____II: Heat is being used to turn solid to __________. (phase change) Q = _____ X _____heat of fusion - _____________ required to change 1g of ___________ to ____________III: Heat is being used to raise the __________ of the _______. Q = ___ X ___ X ____IV: Heat is being used to turn liquid to __________. (phase change) Q = _____ X _____ heat of vaporization - _________ required to change 1 g of _________ to __________V: Heat is being used to raise the temperature of the gas Q=m∆TCpEndothermic change: (_______________ is an example.)• _____________ or ___________ change in which a ____________ absorbs __________ from

its ____________________• ______ → ________ (Heat seems to _________________.)• _____ of system _______________ and it becomes less _____________.(_____________________ is another example.)exothermic change:• physical or chemical ___________ in which a system ____________ ______ heat to its

________________• _____ → _____(Heat seems to ______________ out of _________________ )• _____ of system ______________ and it becomes __________ stable.Ex. - Why does your skin feel cool when you get out of the pool?

Think about these steps to answer the question:Identify the system – _________________ goes from liquid ( ____ P.E.) to ______ ( ____ P.E.).This is an ____________________ change. In this type of change, the system (the water) ___________ heat from the surroundings.Identify the surroundings - ______________Your skin feels __________ because it ___________ heat. The heat was used to _____________ the water.

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Why do farmers spray fruit on trees with water when the temperature is going to drop below freezing? Identify the system and surroundings and make the statements about them (as done above.)_________________________________________________________________________________________________________________________________________________________________________________________________________Energy Diagram of a Chemical Change: Label the chart:

As molecules get closer, their electronclouds _________ each other, and theirP.E. (increases, decreases).The ___________ complex is highest point in P.E.The energy required to reach the complex is called the _____________ energy.Products are (higher, lower) in P.E. than reactants and are (more, less) stable.This reaction is ______thermic.Problem Set #1: Draw the P.E. diagram shown and label the following: reactants, products, activation energy, activated complex, ΔHr (+ or

-)Products are (higher, lower) in P.E. than reactants and are (more, less) stable.This reaction is ______thermic.When Activation energy is high, the reaction is (slow, fast).

HOMEWORK

Label each of the following as "endothermic" or "exothermic":_________ a) Products are more stable than reactants._________ b) Kinetic energy is converted into potential energy._________ c) evaporation_________ d) combustion_________ e) Water freezes.

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_________ f) Heat seems to disappear.

1. a. Calculate the amount of heat released when 25.0 g of water at 25.0°C cools to 0.0°C.

b. Calculate the amount of heat released when the same sample freezes.

2. What is the specific heat capacity of a 35 g sample of an unknown metal that releases 6700 J of heat when it cools from 94 ºC to 29 ºC?

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CHEMISTRY: A Study of Matter Reaction Rates: http://link.brightcove.com/services/player/bcpid9113583001?bctid=1405713920

Note Taking Guide: Episode 1201 reaction rate:

1. the change in _______________ of the ______________ per unit time

2. speed at which ___________ disappear and ___________ appear

The study of reaction rates is called _________________ _____________.

In order for a reaction to occur, reacting ____________ must _____________ effectively.

In an _______________ collision, the ___________ particles collide with the correct _________________ and the proper amount of _____________.

Factors Affecting Reaction Rates:

a. _____________ of reactants-

The ____________ of the reactants, types of _________ involved and state of _____________ all affect reaction rates.

b. _________________ of reactants-

Increasing the concentration of reactants → more ___________ collisions → increased __________ of reaction

Increasing the ___________ of the reactants ( _________ only) → increases the ______________ of reactants → increases ____________________.

c. ______________ of reactants-

increasing __________ of reactants → more _______________________ → increased __________ of reaction.

d. ______________-

a substance that _____________ the rate of a reaction without being permanently ______________

increases the rate of a reaction by __________ the required amount of __________ to achieve ___________ collisions

e. _____________ area of reactants-

increasing surface _________ → more ____________ ____________→ increased __________ of reaction.

CHEMISTRY: A Study of Matter Reaction Rates: http://link.brightcove.com/services/player/bcpid9113583001?bctid=1405713920

1. A study of reaction _______________ is called chemical ________________.

2. Reaction rate refers to how quickly or slowly the _______________ disappear and the _______________ appear. It is measured in terms of the _______________ of the reactants.67

3. If a reaction is to occur, reacting particles must first _______________ and this ______________ must be effective.

What are the TWO characteristics of an effective collision?

4. What are the FIVE major factors that affect reaction rate?

5. Why would a mixture of gases react faster when the volume they occupy is decreased?

6. Why would iron filings rust faster than an iron nail?

7. What is the effect of a catalyst on the required energy to achieve effective collisions?

8. ENZYMES act as catalysts in our bodies. Enzymes are generally made from proteins (amino acid polymer). Have you ever noticed that your hands seem to get “stiff” when they get cold? The reason is that these enzyme reactions causing the muscles to contract __________ down when your hands are cold so you can’t contract your muscles as fast and your hands feel stiff!

Decreasing temperature (decreases, increases) the rate of reaction.

9. Enzymes are in molds and bacteria that spoil food. Explain, using your knowledge of factors affecting the rate of reaction, why food doesn’t spoil as fast when it is refrigerated as it would at room temperature.

10. Due to decomposition reactions with oxygen or carbon dioxide in the air, meat begins to feel slimy and smell spoiled. Explain, using your knowledge of chemical kinetics, why meat spoils less rapidly when left unsliced.

11. Based on your knowledge of factors affecting the rate of reaction, why is there a danger of explosions in places such as silos and coal mines where there are large quantities of powdered, combustible materials?

REACTION RATES AND EQUILIBRIUM VIDEO NOTESLearning Objectives Relate the strength and number of chemical bonds to reaction rates Determine how surface area, concentration and temperature control reaction rates Use Collision Theory to account for the effects of temperature and concentration Account for the action of catalysts in terms of activation energy and alternate reaction

paths Examine choices involved in controlling reaction rates in the Haber Process

Before Viewing

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1. From your experience, give examples of rapid reactions, very slow reactions, speeding up a reaction, and slowing a reaction down

2. Discuss ways in which the rate of a reaction might be measured.

3. Compare and contrast the concepts of strong and weak chemical bonds; ionic and molecular substances

After Viewing1. Why do reactions of ionic substances in solution tend to be rapid at room

temperature?

2. Why are the initial reactants and products enough to describe a reaction?

3. What different ways are commonly used to provide activation energy for combustion?

4. What determines whether a chemical reaction goes to completion?5. What two requirements are essential in producing a chemical product economically?

6. How does equilibrium affect the choice of conditions for the Haber Process?

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a. Write the balanced equation for the production of ammonia from nitrogen and hydrogen

b. Write the equilibrium expression for the forward reaction.

c. The H, enthalpy, for the forward reaction is -92 kJmol-1, what kind of reaction results in this ?

7. How does a catalytic converter and catalytic cracking of petroleum work.

8. List the five factors that affect the rate of a chemical reactiona. b. c. d. e.

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Graphing Heating Curve for water

Water is one of the only substances which is found in three different states or phases on the Earth’s surface. Water changes from a solid to a liquid at 0°C and from a liquid to a gas at 100°C. The data represents the heating of an ice cube of water at -100°C to water vapor at 200°C. As you notice different phases of water heat at different rates. While the water changes phase the temperature of the water stays the same. Create a graph from the data below. Plot time on the X - axis and temperature on the Y - axis. Begin the temperature at -100 and extend it all the way up to +200°C.InterpretationWhat phase of matter is water when the temperature is below 0°C?

What phase of mater is water when the temperature is 50°C?

What phase of matter is water when the temperature is 100°C?

What phase of matter is water when the temperature is 150°C?

Did the water heat faster when it was a solid or a liquid?

What was happening to the water when the temperature was staying constant at 100°?

At what time did the ice begin to melt?

At what time did the water begin to boil?

Once the ice started to melt, how many minutes did it take until the sample was completely liquid?

Explain what is happening to the water molecules in the flat areas of the line on your graph during the phase changes from solid to liquid and liquid to gas.

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

______________________________________________________________________

Timeminute

s

Temperature °C

0 -1001 -502 03 04 05 06 257 508 759 10010 10011 10012 10013 10014 10015 10016 10017 10018 10019 10020 10021 10022 10023 10024 10025 10026 10027 10028 10029 10030 10031 15032 200

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When the ice is melting is it releasing heat or absorbing heat? Explain your answer._____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

If you put the liquid water into the freezer and recorded its temperature as it refroze, would it be absorbing heat or releasing heat? Explain your answer._____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

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GRAPHING REACTION RATES - NY REGENTS PERFORMANCE ASSESSMENT

An experiment is performed to determine how concentration affects the rate of reaction. In each of the four trials equal volumes of solution A and solution B are mixed while the temperature and pressure are held constant. The concentration of solution B is held constant but the concentration of A is varied. The concentration of solution A and the time for the reaction to go to completion for each trial are recorded in the data table.

Which is the independent variable and which was the dependent variable.

Which parameters were controlled?

Describe the relationship between the concentration of solution A and the time for the reaction to go to completion.

Identify one factor, other than the concentration of the solutions, that can affect the rate of reaction.

On the grid below, mark an appropriate scale on the axis that you label “Reaction Time (s)” . On the same grid, plot the data from the data table. Circle and connect the points.

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Trial Concentration of Solution A (M)

Reaction Time (s)

1 0.0200 4.52 0.0150 7.03 0.0100 12.04 0.0050 20.0

Bell Ringers – SHOW WORK

3/28/14 –

How many protons and electrons are in a ion?

Iodine-131 is a radioactive isotope with a half-life of 8 days. How many grams of a 64 g sample of iodine-131 will remain at the end of 24 days?

Which type of nuclear radiation (beta particles, gamma rays, or alpha particles) can be blocked by…a) a piece of paper ________ b) a block of wood ________ c) a piece of lead ____________

4/1/14 What is the volume of a balloon filled with 1 mole of helium gas at STP?

A gas has a volume of 100.0 mL at a pressure of 600.0 mm Hg. If the temperature is held constant, what is the volume of the gas at a pressure of 800.0 mm Hg?

A sample of a gas is in a cylinder as shown. If the temperature is kept constant and the piston moves down to decrease the volume, the pressure increases because the gas particles —

expandlose velocity within the containerbecome smallercollide more frequently with the container

4/2/14 The name of the salt formed by the neutralization of hydrochloric acid and lithium hydroxide is —

An atom contains 70 protons, 70 electrons, and 99 neutrons. What is the mass number and what is the element?Sodium chloride conducts electricity when dissolved in water. What type of bond is present in NaCl?

A student hypothesizes that the solubility of a particular solute in water is nearly constant as temperature varies. The student can best test the hypothesis by doing which of the following?a. Researching the chemical properties of many different solutesb. Measuring the solubility of the solute at five different temperaturesc. Drawing diagrams of the molecular structures of water and of the soluted. Measuring the solubility of several different solutes at a fixed temperature4/4/14 What do the elements sodium (Na) and fluorine (F) have in common?A. Their first ionization energies are similar.B. They are classified as metals.74

C. They are nonreactive.D. The most common ions of each have the same electron configuration.

What is the name of the family that Na is in?What is the name of the group that F is in?

4/7/14 Quiz Which of the following is a solid/solid solution?An alloy of gold and copperA mixture of argon and kryptonA strongly electrolytic acidA neutralized base

Examine the graph of the temperature of a compound versus heat added to the compound. Which of the following most likely happens as the compound is heated from point x to point y?

a. The mass of the compound is increasing.b. The molecules of the compound lose potential energy. c. The phase of the compound changes.d. The molecules of the compound are breaking apart into atoms.

Ionic compounds are useful in conducting electricity when they are dissolved in water. What are such

compounds called?A. metals B. electrolytesC. crystal lattices D. alloys

What is the total number of moles of NaCl(s) needed to make 3.0 liters of a 2.0 M NaCl solution?

4/8/14 – N2 + 3H2 → 2NH3If 6 liters of hydrogen gas are used, how many liters of nitrogen gas will be needed for the above reaction at STP? (fancy mole ratio problem)A 2 liters B 3 litersC 4 litersD 12 liters4/9/14 – When a material freezes, energy A. is absorbed by the material. B. is released by the material.C. is absorbed by a catalyst. D. remains unchanged.

Where is most of the mass of an atom located? A. electrons B. nucleus C. neutrons D. protons

4/10/14 –An acidic solution usually tastes 75

A. bitter. B. salty. C. sour. D. sweet.

A buffer helps to _________A. dissociate an acid. B. dissociate a base. C. neutralize a salt.

D. stabilize pH.

4/11/14 – What is the boiling point of water in kelvins?A. 32 K B. 100 K C. 212 K D. 373 K

Which is always true of an endothermic reaction? A. Chemical bonds are broken. B. Energy is released. C. Light is created. D. Energy is absorbed.

4/22/14 – This is a heating curve for a substance.Between points X and Y, which would be observed?A Solid and liquid will be present.B Only vapor will be present.C Liquid and vapor will be present.D Only liquid will be present.

Identify on the graph all phase changes and the equations to use and where you could use the specific heat equation w/o phase change.

An open container of water is brought to a boil and heated until all of the water is converted to water vapor.Which describes the changes in the water molecules?A The molecules speed up and move farther apart.B The molecules speed up and move closer together.C The molecules slow down and move farther apart.D The molecules slow down and move closer together.

What kind of bond exists between the two nitrogen atoms in N2? A. covalent B. ionic C. metallic D. nuclear

4/23/14 How many particles of NaOH are contained in 80 gram of NaOH

What is the molarity of 80 g of NaOH in 500 mL of solution? A. 2M solutionB. 4M solutionC. 8M solutionD. 40M solution

What is the mass in grams of one mole of any pure substance called?

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A. atomic mass B. average massC. molar mass D. molecular mass

The tarnishing of chrome plated bumpers of antique cars is represented by the following balanced chemical equation. 4Cr(s) +3O2(g) 2Cr2O3(s) What is the mole ratios you would use to predict correctly the number of moles of chromium needed to produce six moles of chromium (III) oxide

4/24/14 – Which of the following is a characteristic common to the alkaline earth metals?A. They easily gain an electron to form ions with a 1- charge.B. They easily gain two electrons to form ions with a 2- charge.C. They easily lose two valence electrons to form ions with a 2+charge.D. They easily lose one valence electron to form ions with a 1+ charge.

A piece of metal is heated in a Bunsen burner flame and then immersed in a beaker of cool water. Which statement best describes the effect of the temperature changes on the kinetic energy of the particles?A Kinetic energy of metal atoms decreases in the flame.B Kinetic energy of water molecules increases when the heated

metal is immersed.C Kinetic energy of water molecules decreases when the heated

metal is immersed.D Kinetic energy of metal atoms increases when immersed in the cooler water.

What is the half-life of a radioisotope if 50.0 grams of an original 200 gram sample of the isotope remains unchanged after 85 years.

4/25/14 –

4/28/14

In the equilibrium reaction: 4HCl (g) + O2 (g) 2H2O (g) + 2Cl2 (g) + 114.4 KJ77

Predict the direction of the equilibrium shift if the following changes occur:The pressure is increased.________________________________________

Energy is added._______________________________________________

Oxygen is added.______________________________________________

HCl is removed._______________________________________________

A catalyst is added.____________________________________________

4/29/14 For the reaction: SiH4(g) + O2(g) SiO2(g) + H2O(g)

a. Write the equilibrium equation:

b. What is Keq if [SiH4] = 0.45M; [O2] = 0.25M; [SiO2] = 0.15M; and [H2O] = 0.10M at equilibrium?

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4/30/14 ReviewIf I have 5.6 liters of gas in a piston at a pressure of 1.5 atm and compress the gas until its volume is 4.8 L, what will the new pressure inside the piston be?

5/1/14 ReviewWhen nitrogen and hydrogen react, they form ammonia gas, which has the formula NH3. If 56.0 g of nitrogen are used up in the reaction, how many grams of ammonia will be produced? Write the equation, balance the equation, convert grams to moles, moles to moles, and then moles to grams.Fe2O3 + 3CO 2Fe + 3CO2 In this reaction, how many grams of Fe2O3 are required to completely react with 84 grams of CO?

5/2/14 NaOH (s) Na+ (aq) + OH- (aq) + 10.6 kcal

Stress Equilibrium Shift

Amount NaOH (s)

[Na+] [OH-] Keq

Add NaOH(s)

Add NaCl

Add KOH

Add H+

Increase T

Decrease T

Increase P

Decrease P

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