Unit 8: Chemical Equilibrium

11. What is the state in which the rate of the forward reaction equals the rate of the reverse reaction called?

a) Dynamic equilibrium
b) Static equilibrium
c) Steady state
d) Homogeneous equilibrium
Answer: a) Dynamic equilibrium

12. Which of the following is true about a reaction at equilibrium?

a) The concentrations of reactants and products are equal
b) The rates of the forward and reverse reactions are equal
c) The reaction has stopped completely
d) Only the forward reaction is occurring
Answer: b) The rates of the forward and reverse reactions are equal

13. What does the equilibrium constant (KcK_cKc​) represent?

a) The rate of the forward reaction
b) The rate of the reverse reaction
c) The ratio of product concentrations to reactant concentrations at equilibrium
d) The temperature of the system at equilibrium
Answer: c) The ratio of product concentrations to reactant concentrations at equilibrium

14. For the reaction aA+bB⇌cC+dDaA + bB \rightleftharpoons cC + dDaA+bB⇌cC+dD, how is the equilibrium constant expression (KcK_cKc​) written?

a) [C]c[D]d/[A]a[B]b[C]^c[D]^d/[A]^a[B]^b[C]c[D]d/[A]a[B]b
b) [A]a[B]b/[C]c[D]d[A]^a[B]^b/[C]^c[D]^d[A]a[B]b/[C]c[D]d
c) [A]a[C]c/[B]b[D]d[A]^a[C]^c/[B]^b[D]^d[A]a[C]c/[B]b[D]d
d) [B]b[D]d/[A]a[C]c[B]^b[D]^d/[A]^a[C]^c[B]b[D]d/[A]a[C]c
Answer: a) [C]c[D]d/[A]a[B]b[C]^c[D]^d/[A]^a[B]^b[C]c[D]d/[A]a[B]b

15. Which of the following does not affect the value of the equilibrium constant (KcK_cKc​)?

a) Temperature
b) Pressure
c) Concentration of reactants
d) Presence of a catalyst
Answer: d) Presence of a catalyst

16. What is the effect of increasing temperature on an exothermic reaction at equilibrium?

a) Shifts equilibrium to the right
b) Shifts equilibrium to the left
c) No effect
d) Increases the equilibrium constant
Answer: b) Shifts equilibrium to the left

17. According to Le Chatelier’s Principle, what happens when the concentration of a reactant is increased in a system at equilibrium?

a) Equilibrium shifts to the right
b) Equilibrium shifts to the left
c) No change in equilibrium position
d) Reaction rate decreases
Answer: a) Equilibrium shifts to the right

18. What is the effect of a catalyst on a reaction at equilibrium?

a) Increases the rate of the forward reaction only
b) Increases the rate of the reverse reaction only
c) Increases the rates of both forward and reverse reactions equally
d) Changes the equilibrium constant
Answer: c) Increases the rates of both forward and reverse reactions equally

19. Which of the following describes the equilibrium position of a reaction with a large KcK_cKc​ value?

a) Reactants are favored
b) Products are favored
c) Reactants and products are present in equal amounts
d) Reaction does not reach equilibrium
Answer: b) Products are favored

20. For the reaction N2(g)+3H2(g)⇌2NH3(g)N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)N2​(g)+3H2​(g)⇌2NH3​(g), what is the effect of increasing pressure?

a) Equilibrium shifts to the right
b) Equilibrium shifts to the left
c) No effect on equilibrium position
d) Decreases the equilibrium constant
Answer: a) Equilibrium shifts to the right