Chapter 16: Chemical Equilibrium (Exam 2) Flashcards Preview

Chemistry 143 > Chapter 16: Chemical Equilibrium (Exam 2) > Flashcards

Flashcards in Chapter 16: Chemical Equilibrium (Exam 2) Deck (11)
Loading flashcards...
1

Law of Mass Action 

aA  + bB -->/

k = [C]c[D]d / [A]a[B]b

Relationship between balanced chemical equation and expression of equilibrium constant  

(rate is same at constant temperature)

2

Significance of Equilbrium Constant

- K > 1 : Forward reaction is favored

- K < 1 : Reverse reaction favored (equilibrium point lies far left)

- K = 1 : Neither direction favored; reaction proceeds halfway

3

Equilibrium Constant (k)

- aA + bB -->/

- k = [C]c[D]d / [A]a[B]b ; products/reactants

- Ratio AT EQUILIBRIUM of concentrations of products raised to stoichiometric coefficients

- Concentration becomes constant and doesn't change once equilbirium has been established

4

Le Chatelier's: Concentration Shifts

- Increase concentration of products (Q < K): Increase concentratino of one or more products causes shift to right

- Increase concentration of one or more products (Q > K): Reaction shifts left

- Decrease concentration of one or more products: Reaction will shift right

- Decrease concentration of one or more reactants: Reaction will shift left

5

Dynamic Equlibrium

Condition in which rate of forward reaction = rate of reverse

- Occurs at same RATE; concentration not same at equilibrium

6

Equilibrium Constant in Terms of Pressure

Kp = Kc(RT)∆n

If total number of moles  = 0; Kp = Kc

7

Le Chatelier's: Change on Equilibrium 

- Exothermic: A + B -->/

- Endothermic: A + B + heat -->/

- Increase in temperature causes exothermic reaction to shift left

- Decrease temperature of exothermic reaction cause shift to right

- Increase temperature of endothermic reaction = shift right

- Decrease temperature of endothermic reaction = shift left

8

Reaction Quotient (Q)

Ratio of concentrations of products raised to stoichiometric coefficients divied by concentration of reactants raised to stoichiometric coefficients (depends on current state of reaction)

- Q < K: Reaction goes right

- Q > K: Reaction goes left

- Q = K: Reaction at equilibrium

9

Le Chatelier's Principle

When chemical system at equilibrium is disturbed, system shifts in direction that minimizes the disturbance

10

Le Chatelier's: Volume Change

- Decrease volume: Shift in direction with fewer moles of GAS

- Increase volume: Shift in direction with greater number of moles of gas particles

- Add inert gas: No effect

- When reaction has equal number of moles on either side of reaction, no effect on equilibrium

11

Reversible Reaction

Can proceed in both forward and reverse reaction