Question 1

A sealed container holds the following reaction at equilibrium: 2NO2(g) ⇌ N2O4(g). If additional NO2(g) is injected into the container, what will happen to the amount of N2O4(g) as the system re-establishes equilibrium?
Correct answer: The amount of N2O4(g) will increase.

Accepted Answer

The amount of N2O4(g) will increase.

Question 2

Which of the following statements about the equilibrium constant (K) is TRUE?
Correct answer: K is calculated using only the concentrations of gases and aqueous species.

Accepted Answer

K is calculated using only the concentrations of gases and aqueous species.

Question 3

For the reaction: H2(g) + I2(g) ⇌ 2HI(g), the equilibrium constant Kc is 50 at 400°C. What does this value of Kc indicate about the composition of the equilibrium mixture?
Correct answer: The mixture contains mostly products.

Accepted Answer

The mixture contains mostly products.

Question 4

Consider the following equilibrium: CaCO3(s) ⇌ CaO(s) + CO2(g). What is the correct expression for the equilibrium constant Kp for this reaction?
Correct answer: Kp = P_CO2

Accepted Answer

Kp = P_CO2

Question 5

A reaction has Δn = 2. If Kc = 0.5 at 298 K, what is the correct relationship for Kp?
Correct answer: Kp = Kc × $$(RT)^2$$

Accepted Answer

Kp = Kc × $$(RT)^2$$

Question 6

A chemical plant operates the exothermic reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g). To maximize SO3 production, which of the following changes should be made?
Correct answer: Decrease temperature and increase pressure.

Accepted Answer

Decrease temperature and increase pressure.

Question 7

Which scenario best illustrates Le Châtelier's Principle?
Correct answer: Adding more reactant to a system at equilibrium causes the system to shift toward products.

Accepted Answer

Adding more reactant to a system at equilibrium causes the system to shift toward products.

Question 8

For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), what will happen to the equilibrium position if the volume of the reaction vessel is halved?
Correct answer: The equilibrium will shift toward the side with fewer moles of gas.

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas.

Question 9

A student writes the following equilibrium expression for the reaction: 2A(g) + B(g) ⇌ 3C(g): K = [C]^3 / ([A]^2 [B]). Which of the following changes would increase the value of K?
Correct answer: Increasing the temperature for an endothermic reaction.

Accepted Answer

Increasing the temperature for an endothermic reaction.

Question 10

If the equilibrium constant for a reaction is 1.0 × 10^-8, which statement is most accurate?
Correct answer: The reaction strongly favors reactants at equilibrium.

Accepted Answer

The reaction strongly favors reactants at equilibrium.

Question 11

Given the following two reactions and their equilibrium constants:
1) A ⇌ B, K1 = 2.0
2) B ⇌ C, K2 = 4.0
What is the equilibrium constant for the overall reaction A ⇌ C?
Correct answer: K = 8.0

Accepted Answer

K = 8.0

Question 12

A reaction mixture at equilibrium contains 0.2 M A, 0.3 M B, and 0.5 M C for the reaction: A + 2B ⇌ 3C. What is the value of Kc?
Correct answer: Kc = $$(0.5)^3 / (0.2$$ × $$(0.3)^2) = 20.8$$

Accepted Answer

Kc = $$(0.5)^3 / (0.2$$ × $$(0.3)^2) = 20.8$$

Question 13

Which of the following changes will NOT affect the position of equilibrium for a reaction involving only gases?
Correct answer: Adding an inert gas at constant volume.

Accepted Answer

Adding an inert gas at constant volume.

Question 14

For the reaction: CO(g) + 2H2(g) ⇌ CH3OH(g), what is Δn for the Kp and Kc relationship?
Correct answer: Δn = -1

Accepted Answer

Δn = -1

Question 15

A hospital stores oxygen gas in a cylinder at equilibrium with solid potassium superoxide (KO2) via the reaction: 4KO2(s) + 2CO2(g) ⇌ 2K2CO3(s) + 3O2(g). If the partial pressure of O2 is increased, what will happen to the amount of CO2(g)?
Correct answer: CO2(g) will decrease.

Accepted Answer

CO2(g) will decrease.

Question 16

Which of the following best describes a heterogeneous equilibrium?
Correct answer: Reactants and products are in different phases.

Accepted Answer

Reactants and products are in different phases.

Question 17

A reaction at equilibrium is endothermic. What will happen to the equilibrium constant K if the temperature is increased?
Correct answer: K will increase.

Accepted Answer

K will increase.

Question 18

For the reaction: 2A(g) ⇌ B(g) + C(g), the equilibrium concentrations are [A] = 0.4 M, [B] = 0.2 M, [C] = 0.2 M. What is the value of Kc?
Correct answer: Kc = (0.2 × 0.2) / $$(0.4)^2 = 0.25$$

Accepted Answer

Kc = (0.2 × 0.2) / $$(0.4)^2 = 0.25$$

Question 19

Which of the following is a correct statement about the effect of a catalyst on a system at equilibrium?
Correct answer: A catalyst speeds up the attainment of equilibrium but does not change the equilibrium position.

Accepted Answer

A catalyst speeds up the attainment of equilibrium but does not change the equilibrium position.

Key Concepts in Chemical Equilibrium

Study Guide - Practice Questions

Study Guide - Flashcards