Chapter 16: Chemical Equilibrium (Exam 2)

Question 1

Law of Mass Action

aA + bB –>/<– cC + dD

Answer 1

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)

Question 2

Significance of Equilbrium Constant

Answer 2

• K > 1 : Forward reaction is favored
• K < 1 : Reverse reaction favored (equilibrium point lies far left)
• K = 1 : Neither direction favored; reaction proceeds halfway

Question 3

Equilibrium Constant (k)

Answer 3

• aA + bB –>/<– cC + dD
• 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

Question 4

Le Chatelier’s: Concentration Shifts

Answer 4

• 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

Question 5

Dynamic Equlibrium

Answer 5

Condition in which rate of forward reaction = rate of reverse

• Occurs at same RATE; concentration not same at equilibrium

Question 6

Equilibrium Constant in Terms of Pressure

Answer 6

K_p = Kc(RT)^∆n

^- If total number of moles = 0; Kp = Kc

Question 7

Le Chatelier’s: Change on Equilibrium

Answer 7

• Exothermic: A + B –>/<– C + D + heat
• Endothermic: A + B + heat –>/<– C + D
• 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

Question 8

Reaction Quotient (Q)

Answer 8

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

Question 9

Le Chatelier’s Principle

Answer 9

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

Question 10

Le Chatelier’s: Volume Change

Answer 10

• 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

Question 11

Reversible Reaction

Answer 11

Can proceed in both forward and reverse reaction