Transcript of Drill #12 5/13, 14/2014 Write the balanced neutralization equations for the following reactions: 1....
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- Drill #12 5/13, 14/2014 Write the balanced neutralization
equations for the following reactions: 1. carbonic acid &
calcium hydroxide 2. potassium hydroxide and carbonic acid 3.
barium hydroxide and hydrochloric acid
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- Drill #12 5/13, 14/2014 Write the balanced neutralization
equations for the following reactions: 1. H 2 CO 3 +CA(OH) 2
===> CaCO 3 +2H 2 O 2. 2 KOH + H 2 CO 3 ===> K 2 CO 3 + 2H 2
O 3. Ba(OH) 2 + 2HCl ===> BaCl 2 + 2H 2 O
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- Objectives SWBAT describe the concept of chemical equilibrium
and explain how and when it is achieved. SWBAT write an equilibrium
expression. SWBAT describe the progress of a chemical reaction by
using the equilibrium constant. SWBAT explain how physical changes
such as concentration, pressure, and temperature can affect a
chemical reaction at equilibrium.
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- Agenda Equilibrium notes Equilibrium lab Review Worksheets
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- CHEMICAL EQUILIBRIUM
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- Up to this point we have mostly been considering reactions to
completion, where all the reactants change into product. reversible
However, most reactions are reversible = occurs in both the forward
and the reverse directions.
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- N 2 (g) + 3H 2 (g) 2NH 3 (g) forward N 2 (g) + 3H 2 (g) 2NH 3
(g) reverse N 2 (g) + 3H 2 (g) 2NH 3 (g) or N 2 (g) + 3H 2 (g) 2NH
3 (g) Combined in one equation using double arrows
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- Chemical Equilibrium A state in which the forward and reverse
reactions balance each other and when the forward reaction proceeds
at the same rate as the reverse reaction. Concentrations of
reactants and products are constant at equilibrium. (Constant
equal)
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- Rate vs. Time
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- Equilibrium Lab Work in pairs Read directions first then follow
directions carefully Answer questions 1-4 for homework
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- Equilibrium constant Kequilibrium constant K is called the
equilibrium constant. It is a ratio of the concentrations of
products to the concentration of reactants.
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- Equilibrium Constant Expression aA + bB cC + dD K eq = [C] c
[D] d [A] a [B] b A & B = molar [ ] of reactants C & D =
molar [ ] of products Exponents a, b, c, and d = coefficients in
the balanced equation.
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- Equilibrium Constant K eq > 1 If K eq > 1: products are
favored at equilibrium If K eq < 1 If K eq < 1: reactants are
favored at equilibrium
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- Important! Only substances that are gases and aqueous get
factored into the equilibrium expression Pure liquids and solids do
not appear in the expression.
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- Example #1 Write the equilibrium expression for the following
reaction: 2 CO (g) + O 2 (g) 2 CO 2 (g)
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- Answer K eq = [CO 2 ] 2 / ([CO] 2 [O 2 ])
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- Example #2 Write the equilibrium expression for the following
reaction: CO (g) + 3 H 2 (g) CH 4 (g) + H 2 O (g)
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- Answer K eq = [CH 4 ][H 2 O] / ([CO][H 2 ] 3 )
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- Assignment Complete Equilibrium Constant WS #1-5
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- Drill #13 5/15, 19/2014 What is the pH of a 2.23 x 10 -6 M
solution of HI? What is the pH and pOH of a 2.34 x 10 - 5 M NaOH
solution?
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- Drill #13 5/15, 19/2014 What is the pH of a 2.23 x 10 -6 M
solution of HI? Ans: pH = 5.65 What is the pH and pOH of a 2.34 x
10 -5 M NaOH solution? Ans: pOH = 4.63, pH = 9.38
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- Agenda Acids and Bases Test Le Chatelier Principle Homework Le
Chateliers Worksheet (given to you last class)
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- Homework Due: Bean Lab Equilibrium Constant WS
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- Important! Changes to Test 7. In the titration of a solution of
Sr(OH) 2 with HCl, the mole ratio of base to acid a.) is 1:1 c.) is
2:1 b.) is 1:2 d.) cannot be determined 10. An Arrhenius acid is
a(an) a.) a substance that reacts with a salt. b.) substance that
donates a H+ ion when combined with a base. c.) substance that
releases H+ ions in an aqueous solution. d.) substance that
releases OH- ions in a aqueous solution.
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- LE CHTELIERS PRINCIPLE
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- Question Can we change the equilibrium position thereby
increasing the amount of products in a reaction? adding stress Yes
by adding stress to a system in equilibrium.
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- Le Chteliers Principle stress is applied relieves the stress.
If a stress is applied to a system at equilibrium, the system
shifts in the direction that relieves the stress. Stress is
anything that upsets equilibrium changes in concentration,
pressure, or temperature.
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- Concentration Measure of molarity (moles/L) If you
concentration of a reactant, equilibrium will shift toward the
products. If you concentration of a reactant, equilibrium will
shift toward the reactants.
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- CO(g) + 3H 2 (g) CH 4 (g) + H 2 O(g) CO(g) H 2 O(g)
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- Changes in Concentration A + B C + D Increasing the
concentration of A will shift the reaction to the right we need to
get rid of excess A Decreasing the concentration of C will shift
the reaction to the right there is a deficit, so more C needs to be
made
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- Temperature Increasing the temperature shifts the reaction away
from the side that contains the heat Decreasing the temperature
shifts the reaction toward the side that contains the heat
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- Temperature Think of heat as a reactant or a product. CO(g) +
3H 2 (g) CH 4 (g) + H 2 O(g) + heat Is this Exothermic or
Endothermic?
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- heat CO(g) + 3H 2 (g) CH 4 (g) + H 2 O(g) + heat
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- Sample Reaction heat + NH 4 Cl (s) NH 3 (g) + HCl (g)
endothermicIn the above endothermic reaction, increasing the
temperature will drive the reaction to the right (in other words,
forward)
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- Pressure PV=nRTIdeal Gas Law: PV=nRT If P then n, which means
more number of atoms. If P, then the equilibrium will shift toward
the side with fewer moles of gas.
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- CO(g) + 3H 2 (g) CH 4 (g) + H 2 O(g) 4 moles of gas 2 moles of
gas Note: If moles of gaseous reactant = moles of gaseous product,
then no shift in equilibrium will occur from a change in
pressure
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- Le Chteliers Principle If a stress is applied to a system at
equilibrium, the system shifts in the direction that relieves the
stress. Concentration Pressure Temperature Note: Only temperature
affects K. The larger the value of K, the more product at
equilibrium.
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- Assignment Le Chteliers Principle Worksheet
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- Wrap up K eq > 1 If K eq > 1: are favored at equilibrium
If K eq < 1 If K eq < 1: are favored at equilibrium
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- Drill #14May 19 & 20, 2014 What are the 3 types of stress
that can affect the equilibrium of a system? Which states of matter
get factored into an equilibrium expression?
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- Agenda Go over Equilibrium Worksheet Notes on Equilibrium
Problems Complete the following worksheets: 16-3 Review and
Reinforcement 2 Equilibrium Worksheets handed out to you by
sub
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- Announcement!! Wear closed-toed shoes next class. We will be in
the lab!
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- DIFFERENT TYPES OF EQUILIBRIUM
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- Concentration Equilibrium K c (or K eq ) nA + mB xC + yD K c =
[C] x [D] y [A] n [B] m
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- Rememberequilibrium is where the rates of forward and reverse
reactions are the same. It means that the concentrations do not
change, NOT that they are identical.
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- Because equilibrium expressions have to do with concentration
(in molarity) we do not include items that are not in solution so
NO LIQUID or SOLID states! They are in excess so can be
ignored.
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- Acid Equilibrium Acid + H 2 O H 3 O + + Acid Ion or HA + H 2 O
H 3 O + + A - K a = [H 3 O + ][A - ] [HA][H 2 O] [HA] Because water
is a solvent and its conc. greatly exceeds the acid, we can assume
that the conc. of water does not change.
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- Base Equilibrium Base + H 2 O OH - + Base Ion or B + H 2 O OH -
+ HB + K b = [OH - ][HB + ] [B][H 2 O] [B]
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- PropertyStrong AcidWeak Acid K a valueK a is largeK a is small
Position of equilibrium Far to the right (a lot of dissociation)
Far to the left (little dissociation) [H+] compared to original
[HA] [H+][HA] o [H+]