Chapter 13

Properties of Solutions: Most things in life are solutions. Get with the program.

February 13th, 2013

Do Now: Clear desk except for a writing utensil-

Intermolecular Forces Quiz

Definitions GALORE

Define the following words with a neighbor: Solvent: Solute: Aqueous solution: Entropy: Spontaneous:

Ammonium Nitrate + Water

Predict the resulting reaction for Ammonium Nitrate and Water

Do we expect this process to be endothermic or exothermic? Why?

Why is this reaction surprising?

What can we ask for the aim today?

Natural Abilities

How is the ability of a substance to form a solution affected? Types of I.M.F in solution process Natural tendency of substances to mix/spread

when not restrained Why is the mixing of gases a spontaneous

process? No energy input from outside the system

Why is it important to discuss entropy in solution? Increase in entropy is favored in solutions

Explain why NaCl mixes in water and not gasoline.

Show me the money! $$$$

…furthermore.

Three types of intermolecular attraction in solution formation: Solute-solute: interactions between molecules of

solute must be overcome to disperse solute Solvent-solvent: interactions between solvent

molecules must be overcome to make way for solute Solvent-solute: occur as particles mix

In terms of intermolecular attraction, what must be true in order for a solution to form?

In terms of intermolecular attractions, explain why heptane and pentane can mix.

Water + NaCl

Write a paragraph explaining why NaCl is able to dissolve in water. Include the following terms: Solvent-solute Solute-solute Solvent-solvent Ion-dipole attraction

Define: Solvation: Hydration:

So what you’re saying is…

As we experienced in our demo, solution processes generally are accompanied by:

How might we be able to determine how the interactions in the solution influence enthalpy?

Formulate an equation to calculate ∆Hsoln

February 14th, 2013

Do Now: Write a paragraph explaining why

NaCl is able to dissolve in water. Include the following terms: Solvent-solute Solute-solute Solvent-solvent Ion-dipole attraction

…Hess, you’ve come back!

Predict for each of the three types of interactions whether or not they are endothermic or exothermic. Explain your reasoning.

Why is enthalpy useful to us in determining extent of reaction?

How picturesque

Solution formation vs. Chemical Reactions

How is forming a solution different than a chemical reaction?

Define dissolution:

What does this suggest for our aim?

Noooooooo….more……please!

Is your brain saturated yet? How about super-saturated?

On the molecular level, explain the interactions of solute and solvent as concentration increases.

Define the following terms with a neighbor: Saturation: Unsaturated: Supersaturation: Solubility

Explain the trend:

How does solubility of gas relate to intermolecular forces?

Why is acetone soluble?

Mis-a-what?

How do we differentiate between miscible and immiscible?

How can we alter hexane to make is miscible? Explain in terms of attraction.

Predict the trend:

**Hint: how does the number of carbons affect solubility in water?

February 15th, 2013

DO NOW: Predict whether each of the following

substances is more likely to dissolve in the solvent carbon tetrachloride or water: C7H16 Na2SO4 HCl I2

Arrange the following in order of increasing solubility in water (explain your reasoning *psst..

Please actually write the reason in your notebook.**): c5H11OH, c5H12, c5H11Cl, c5H10(OH)2

Welp…

As the world is evolving, the number of habitable lakes for wildlife is slowly declining.

Predict the trend between pressure and solubility. Can you think of an example?

Explained.

At equilibrium, rate of gas molecules entering and leaving solution is equal. Exert pressure: what happens to the

rate at which molecules are colliding with the surface?

How can we relate this to the partial pressure of gas? Solubility of gas in a liquid solvent

increases in direct proportion to partial pressure of gas.

Henry’s Law

Relationship between pressure and gas solubility:

Sg = kPg

Sg= solubility of the gas in the solvent (usually expressed as molarity)

Pg= partial pressure of the gas over solution

k= proportionality constant (Henry’s Law Constant)

**k depends on solute, solvent, and temp.

অনু�শী�লনু (Bengali)

Calculate the concentration of CO2 in a soft drink that is bottled with a partial pressure of 4.0 atm over the liquid at 25 degrees celcius. The Henry’s law constant for CO2 in water at this temperature is 3.4 x 10-

2 mol/L-atm

Temperature Effects

As temperature increases, the solubility of most solid solutes increases. How do you think gas solubility is effected by temperature?

Think about it…

Why do bubbles form on the inside of the cooking pot when water is heated on a stove, even though the water temperature is well below the boiling point?

Well how do we represent concentration?

How can we differentiate between mass percentage, ppm, and ppb?

When would we use ppm or ppb?

IE: toxic concentrations expressed in ppm or ppb: Max allowable concentration of arsenic in

drinking water is 0.010 ppm. How do we express this in grams?

Практика (Bulgarian)

A solution is made by dissolving 13.5 g of glucose in 0.100 kg of water. What is the mass percentage of solute in this solution?

A 2.5 gram sample of groundwater was found to contain 5.4 microliters of zinc 2+. What is the concentration of Zn 2+ in ppm?

February 20th, 2013

Do Now: Calculate the mass percentage of NaCl

in a solution containing 1.50 g of NaCl in 50.0 g of H2O.

A commercial bleaching solution contains 3.62% by mass sodium hypochlorite (NaOCl). What is the mass of NaOCl in 2.50 kg of bleaching solution?

What does this suggest for our aim?

3.0 Molar

3.0 Molal

Molarity, Molality, and Mole fractions: Oh My!

How do we express mole fractions? IE: Solution contains 1.00 mol of HCl +

8.00 mol of H2O. What is the mole fraction of HCl?

How do we express Molarity? IE: What is the molarity of a solution with

0.50 mol of solute in 0.250 L solution?How do we express molality?

IE: 0.200 mols of NaOH is mixed with 0.500 kg of H2O. What is the concentration?

…huh?

How can we differentiate between molality and molarity?

**Note: when water is solvent, the 2 numbers will be very similar. Why?

Why do we use molality when varying temperature of solution?

Pràctica (Catalan)

A solution is made by dissolving 4.35 g of glucose in 25 mL of H2O @ 25 degrees celcius. Calculate the molality.

What is the molality of a solution made by dissolving 36.5 g of Naphthalene (C10H5) in 425 g of Toluene (c7H8)?

Converting Units

Sometimes it is necessary to interconvert units when given a different unit.

IE: An aqueous solution of HCl contains 36% HCl by mass.

Molal/Molar Conversions

A solution with a denistry of 0.876 g/mL contains 5.0 g of Toluene and 225 g of Benzene. Calculate the molarity.

Conversion Chart

实践 (Chinese- simplified)

Remember that worksheet you were given for homework? Time to go take another look at it…

February 21st, 2013

Do now:

A solution containing equal masses of glycerol (C3H8O3) and water has a density of 1.10 g/ml. Calculate:▪ The molality of glycerol▪ The mole fraction of glycerol▪ The molarity of glycerol

So, why do properties of solutions change?

Define Colligative Properties: Properties of solvents that depend on

total concentration of solute particles present

Give Examples of Colligative Properties: Vapor-Pressure Lowering Freezing Point Lowering Boiling Point Elevation Osmotic Pressure

Vapor-Pressure

Redefine the following words in terms of vapor pressure: Vapor Pressure: Volatile: Non-volatile:

Describe what would happen if you added a nonvolatile solute to a volatile solvent.

Visualize this!

Explain this visual.

Raoult’s Law

Vapor pressure of solution containing non-volatile solue/volative solvent is proportional to solvent concentration

How do we express this qualitatively?

IE: Vapor pressure of water @ 20 degrees Celsius is 17.5 torr. If temp is held constant and sugar is added, mol fraction of water is XH2O= 8.00. How does the addition of glucose effect the vapor pressure?

实践 (Chinese- Simplified)

Glycerine- a nonvolatile nonelectrolyte with a density of 1.26 g/ml is used to make a solution with 50.0 mL glycerine with 500.0 mL water. At 25 degrees Celsius, the vapor pressure of water is 23.8 torr and density is 1.00 g/ml.

Una Mas.

The vapor pressure of pure water at 110 degrees Celsius is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1.00 atm at 110 degrees Celsius. What is the mole fraction of ethylene glycol?

February 22, 2013

Do Now: Calculate the Vapor Pressure of water

above a solution prepared by adding 22.5 g of lactose (C12H22O11) to 200.0 g of water at 338 K. (pure water = 187.5 torr)

Calculate the mass of propylene glycol (C3H8O2) that must be added to 0.340 kg of water to reduce the vapor pressure by 2.88 torr at 40 degrees Celsius. (pure water = 55.3 torr)

Ideal Solutions

Using prior knowledge, how might we relate the concept of an ideal gas to that of an ideal solution?

Explain what this means for solute-solute, solvent-solvent, and solute-solvent interactions.

** Be aware, not all solutions are “ideal” will be discussed in later chapters.

Boiling Point

If the addition of non-volatile solute lowers vapor pressure, how is the boiling point effected?

Numerically speaking…

How can we represent the increase in boiling point numerically?

IE: NaCl is dissolved in water. A 1 molal solution is created. Calculate the boiling point elevation of the solution.

Summarize: A solute dissolved in water causes the boiling point to increase by 0.51 degrees celsius. Does this necessarily mean that the concentration of the solute is 1.0 m? Explain.

Explain the phenomena

Freezing Point

How do we determine the freezing point of a liquid?

How is freezing point effected when creating solutions? Explain.

Calculation time!

How might we calculate the change in freezing point?

IE: Automotive antifreeze consists of ethylene glycol, CH2(OH)CH2(OH), a nonvolatile nonelectrolyte. Calculate the boiling point and greezing point of a 25.0 mass % solution of ethylene glycol in water. (Kb= 0.51 C/m) (Kf= 1.86 C/m)

February 28th, 2013

Which of the following solutes will produce the largest increase in boiling point upon addition to 1 kg of water and why Co(NO3)2

2 mol of KCl 3 mol of ethylene glycol (C2H6O2)

Osmosis

Define semipermeable

Define Osmosis Why does osmosis take place?

*note: rate at which solvent passes from less concentrated solution (lower solute, higher solvent) to more concentrated solution is greater than the rate in the opposite direction

Osmot-a-what?

Define Osmotic Pressure:

Application

Similar to ideal gas law:∏ = (n/V)RT

∏ = osmotic pressureV= volume of the solution

n= number of moles of soluteR = ideal gas constant

T = temperature in Kelvin How can we change the equation to

include Molarity?

Behind door 1…

Using these diagrams and the concept of osmotic pressure, label and define which of these are isotonic, hypotonic, and hypertonic.

Cells? Why in Chemistry…

Describe what would happen if a red blood cell was placed in a solution that is hypertonic relative to the intracellular solution. Crenation: process in which a cell

shrivels

Describe what would happen if the cell is hypotonic relative to intracellular fluids. Hemolysis: process of cell repture

Praksa (Croatian)

The average osmotic pressure of blood is 7.7 atm @ 25 degrees celsius. What molarity of glucose will be isotonic with blood?

What is the osmotic pressure at 20 degrees Celsius of a 0.0020 M sucrose solution? (C12H22O11)

Determination of Molar mass

Any of the four colligative properties can be used to determine molar mass:

1. Freezing Point Depression/ Boiling Point Elevation:▪ A solution of unknown solute was prepared by

dissolving 0.250 g of the substance in 40.0 g of CCl4. The resultant boiling point of the solution was 0.357 degrees higher than that of the pure solvent. Calculate the molar mass.

Determination of Molar Mass Cont.

Osmotic Pressure: The osmotic pressure of an aqueous

solution of a certain protein was measured to determine the proteins molar mass. The solution contained 3.50 mg of protein dissolved in sufficient water to form 5.00 mL of solution. The osmotic pressure of the solution at 25 degrees celsius was found to be 1.54 torr. Calculate the molar mass.

cvičit (czech)

Camphor (C10H16O) melts at 179.8 degrees Celsius and it has a large Kf= 40.0 C/m. When 0.186 g of an organic substance of unknown molar mass is dissolved in 22.01 g of liquid camphor, the freezing point is found to be 176.7. What is the molar mass?

A sample of 2.05 g of polystyrene of uniform polymer chain length was dissolved in enough toluene to form 0.100 L of solution. The osmotic pressure of the solution was found to be 1.21 kPa at 25 degrees Celsius. Calculate the molar mass.