chapter 13.1-13.4 ap chem chemical equilibrium. 2 chapter 13 table of contents copyright © cengage...

Chapter 13.1-13.4AP Chem

Chemical Equilibrium

2

Chapter 13

Table of Contents

Copyright © Cengage Learning. All rights reserved

13.1The Equilibrium Condition

13.2The Equilibrium Constant

13.3Equilibrium Expressions Involving Pressures

13.4Heterogeneous Equilibria

13.5Applications of the Equilibrium Constant

13.6 Solving Equilibrium Problems

13.7 Le Châtelier’s Principle

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Chapter 13

Table of Contents


• WEEK OUTLOOK• Monday - Notes 13.1-13.4 with problems w/sheet due

Tuesday - should be able to complete in class today.• *Be sure all reports are turned in and made up TODAY!• Tuesday - Notes 13.5-13.7 with emphasis on Le

Chatelier’s Principle emphasized & problems assigned due Wed. - some time in class to complete

• Kaci & Jonathan - library 2nd floor 7:30 with ACT invent.• Wednesday- Lab• Thursday - CAPS - No class• Friday - Good Friday - No school• Tuesday - April 2nd - ACT Testing 11th graders only.• Test probably next Thursday - just over ch. 13 only.

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4

Chapter 13

Table of Contents


• HANDOUTS - Ch. 13 NMSI Equilibrium Packet (Notes with practice problems)

• HANDOUT - Equilibrium Homework Sheet #1

• TURN IN Kinetics Lab - will go over pre-lab questions• HW: Equilibrium w/s #1 should be done today - due

Mon. for grade• HW: Notes packet #1-6 problems due next week but

keep for studying.• CW: Notes 13.1-13.4 • VOTE ON KINETICS TESTING CH. 12• Iodine Clock Rxn. Simulation Lab - as time permits

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Chapter FourteenGeneral Chemistry 4th edition, Hill, Petrucci, McCreary, PerryPrentice Hall © 2005Hall © 2005

Dynamic Nature of Equilibrium

When a system reaches equilibrium, the forward and reverse reactions continue to occur … but at equal rates.

We are usually concerned with the situation after equilibrium is reached.

After equilibrium the concentrations of reactants and products remain constant.

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Section 13.1

The Equilibrium Condition


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• The state where the concentrations of all reactants and products remain constant with time.

• On the molecular level, there is frantic activity. Equilibrium is not static, but is a highly dynamic situation.

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Section 13.1



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Equilibrium Is:

• Macroscopically static • Microscopically dynamic

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Section 13.1



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Changes in Concentration

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

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Section 13.1



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• Concentrations reach levels where the rate of the forward reaction equals the rate of the reverse reaction.

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Section 13.1



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The Changes with Time in the Rates of Forward and Reverse Reactions

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Section 13.1



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Concept Check

Consider an equilibrium mixture in a closed vessel reacting according to the equation:

H2O(g) + CO(g) H2(g) + CO2(g)

You add more H2O(g) to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is reestablished? Justify your answer.

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Section 13.1



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Concept Check

Consider an equilibrium mixture in a closed vessel reacting according to the equation:

H2O(g) + CO(g) H2(g) + CO2(g)

You add more H2 to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is reestablished? Justify your answer.

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Section 13.2

Atomic Masses


The Equilibrium Constant

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Consider the following reaction at equilibrium:

jA + kB lC + mD

• A, B, C, and D = chemical species.

• Square brackets = concentrations of species at equilibrium.

• j, k, l, and m = coefficients in the balanced equation.

• K = equilibrium constant (given without units).

j

l

k

m

[B][A]

[D] [C]K =

Law of Mass ActionLaw of Mass Action

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Section 13.2

Atomic Masses



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Conclusions About the Equilibrium Expression

• Equilibrium expression for a reaction is the reciprocal of that for the reaction written in reverse.

• When balanced equation for a reaction is multiplied by a factor of n, the equilibrium expression for the new reaction is the original expression raised to the nth power;

• thus Knew = (Koriginal)n.

• K values are usually written without units.

Conclusions about Equilibrium Conclusions about Equilibrium ExpressionsExpressions

The equilibrium expression for a reaction The equilibrium expression for a reaction is the reciprocal for a reaction written in is the reciprocal for a reaction written in reversereverse

2NO2NO22(g) (g) 2NO(g) + O 2NO(g) + O22(g(g))

2NO(g) + O2NO(g) + O22(g) (g) 2NO2NO22(g)(g)

Conclusions about Equilibrium Conclusions about Equilibrium ExpressionsExpressions

When the balanced equation for a reaction When the balanced equation for a reaction is multiplied by a factor is multiplied by a factor nn, the equilibrium , the equilibrium expression for the new reaction is expression for the new reaction is the the original expressionoriginal expression, raised to the , raised to the nthnth power. power.

2NO2NO22(g) (g) 2NO(g) + O 2NO(g) + O22(g(g))

NONO22(g) (g) NO(g) + ½O NO(g) + ½O22(g(g))

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Section 13.2

Atomic Masses



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• K always has the same value at a given temperature regardless of the amounts of reactants or products that are present initially.

• For a reaction, at a given temperature, there are many equilibrium positions but only one value for K. Equilibrium position is a set of equilibrium

concentrations.

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Section 13.3

The Mole Equilibrium Expressions Involving Pressures


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• K involves concentrations - (also called Kc)

• Kp involves pressures for gases.

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Section 13.3



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Example

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

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Section 13.3



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Example

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

Equilibrium pressures at a certain temperature:

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Section 13.3



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Example

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

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Section 13.3



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The Relationship Between K and Kp

Kp = K(RT)Δn

• Δn = sum of the coefficients of the gaseous products minus the sum of the coefficients of the gaseous reactants.

• R = 0.08206 L·atm/mol·K• T = temperature (in kelvin)

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Section 13.3



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Example

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

Using the value of Kp (3.9 × 104) from the previous example, calculate the value of K at 35°C.

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Section 13.4

Heterogeneous Equilibria


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Homogeneous Equilibria

• Homogeneous equilibria – involve the same phase:

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

HCN(aq) H+(aq) + CN-(aq)

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Section 13.4



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• Heterogeneous equilibria – involve more than one phase:

2KClO3(s) 2KCl(s) + 3O2(g)

2H2O(l) 2H2(g) + O2(g)

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Section 13.4



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• The position of a heterogeneous equilibrium does not depend on the amounts of pure solids or liquids present. The concentrations of pure liquids and solids

are constant.

2KClO3(s) 2KCl(s) + 3O2(g)

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Chapter FourteenGeneral Chemistry 4th edition, Hill, Petrucci, McCreary, PerryPrentice Hall © 2005Hall © 2005

Equilibria Involving PureSolids and Liquids

• The equilibrium constant expression does not include terms for pure solid and liquid phases because their concentrations do not change in a reaction.

• Although the amounts of pure solid and liquid phases change during a reaction, these phases remain pure and their concentrations do not change.

[CaO] [CO2]Kc = –––––––––– [CaCO3]

Kc = [CO2]

Example: CaCO3(s) CaO(s) + CO2(g)

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Section 13.4



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ASSIGNMENTS - 2/20/14

• W/sheet #1 problems due Monday • This assignment should be able to be completed today

in class but is due Monday.

• Ch. 13 Equilibrium packet - #1-#6 practice problems - answers shown to see if you are doing correctly.

• Prepare for Test on Kinetics.• HW: Read chapter 13 over the next week.

• Ch. 12 Kinetics Test - VOTED for WEDNESDAY - Feb 26

chapter 13.1-13.4 ap chem chemical equilibrium. 2 chapter 13 table of contents copyright © cengage...

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