Question 1

A sealed container contains the following reaction at equilibrium: N2(g) + 3H2(g) ⇌ 2NH3(g). If additional H2(g) is injected into the container, what will happen to the system according to Le Châtelier’s Principle?
Correct answer: The reaction will shift to the right, producing more NH3.

Accepted Answer

The reaction will shift to the right, producing more NH3.

Question 2

For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), the equilibrium constant Kp is 4.0 at a certain temperature. If the partial pressures are [SO2] = 0.50 atm, [O2] = 0.20 atm, and [SO3] = 0.80 atm, what is the value of the reaction quotient Qp, and in which direction will the reaction proceed?
Correct answer: Qp = 12.8; reaction will proceed in reverse (toward reactants).

Accepted Answer

Qp = 12.8; reaction will proceed in reverse (toward reactants).

Question 3

Which of the following statements about the equilibrium constant (K) is correct?
Correct answer: K is only affected by temperature changes.

Accepted Answer

K is only affected by temperature changes.

Question 4

A reaction has a standard Gibbs free energy change (ΔG°) of -25 kJ/mol at 298 K. Which statement is true about the equilibrium constant (K) for this reaction at 298 K?
Correct answer: K is much greater than 1, favoring product formation.

Accepted Answer

K is much greater than 1, favoring product formation.

Question 5

Consider the following two-step reaction mechanism:
Step 1: A ⇌ B, K1 = 2.0
Step 2: B ⇌ C, K2 = 5.0
What is the equilibrium constant for the overall reaction A ⇌ C?
Correct answer: K = 10.0

Accepted Answer

K = 10.0

Question 6

A patient is given a drug that is a weak acid. In the bloodstream, the following equilibrium is established:
HA ⇌ H+ + A−
If the patient is given a medication that increases blood pH, what will happen to the concentration of HA?
Correct answer: The concentration of HA will increase.

Accepted Answer

The concentration of HA will increase.

Question 7

For the reaction 2NO2(g) ⇌ N2O4(g), the equilibrium constant expression is:
Correct answer: K = [N2O4]/[NO2]^2

Accepted Answer

K = [N2O4]/[NO2]^2

Question 8

A chemical reaction has ΔG = 0. What can be concluded about the system?
Correct answer: The system is at equilibrium.

Accepted Answer

The system is at equilibrium.

Question 9

Which of the following changes will NOT affect the position of equilibrium for a reaction in a closed system?
Correct answer: Adding a catalyst.

Accepted Answer

Adding a catalyst.

Question 10

A reaction mixture initially contains only reactants. As the reaction proceeds, the value of Q increases until it equals K. What does this indicate about the system?
Correct answer: The system is approaching equilibrium as products form.

Accepted Answer

The system is approaching equilibrium as products form.

Question 11

For the gas-phase reaction: 2A(g) + B(g) ⇌ 3C(g), which of the following is the correct equilibrium constant expression in terms of partial pressures?
Correct answer: Kp = $$(PC)^3$$ / [$$(PA)^2 * PB$$]

Accepted Answer

Kp = $$(PC)^3$$ / [$$(PA)^2 * PB$$]

Question 12

A reaction at equilibrium is subjected to a sudden increase in pressure by decreasing the volume. Which direction will the equilibrium shift if the number of moles of gas is greater on the reactant side?
Correct answer: Toward the product side (fewer moles of gas).

Accepted Answer

Toward the product side (fewer moles of gas).

Question 13

If the reaction quotient Q is less than the equilibrium constant K, what does this imply about the concentrations of reactants and products?
Correct answer: There are more reactants than at equilibrium; the reaction will proceed forward.

Accepted Answer

There are more reactants than at equilibrium; the reaction will proceed forward.

Question 14

A student claims that adding more product to a reaction at equilibrium will increase the value of the equilibrium constant. Is this correct?
Correct answer: No, the equilibrium constant is only affected by temperature.

Accepted Answer

No, the equilibrium constant is only affected by temperature.

Question 15

For the reaction: CO(g) + 2H2(g) ⇌ CH3OH(g), the equilibrium constant Kc is 0.50 at a certain temperature. If [CO] = 0.20 M, [H2] = 0.10 M, and [CH3OH] = 0.05 M, what is the value of Qc and which way will the reaction shift?
Correct answer: Qc = 2.5; reaction will shift toward reactants.

Accepted Answer

Qc = 2.5; reaction will shift toward reactants.

Question 16

Which of the following best describes the relationship between ΔG°, K, and temperature (T)?
Correct answer: K = exp(−ΔG°/RT)

Accepted Answer

K = exp(−ΔG°/RT)

Question 17

A reaction has K = 1.0 × 10^−8 at 25°C. Which statement is true about the composition of the equilibrium mixture?
Correct answer: The mixture contains mostly reactants.

Accepted Answer

The mixture contains mostly reactants.

Question 18

A reversible reaction is at equilibrium in a closed container. If some of the product is removed, what will happen to the reaction?
Correct answer: The reaction will shift forward to produce more product.

Accepted Answer

The reaction will shift forward to produce more product.

Chemical Equilibrium and Le Châtelier’s Principle

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