Question 1

A chemical reaction is at equilibrium in a closed container. If additional reactant is suddenly added, which of the following will occur according to Le Châtelier’s Principle?
Correct answer: The reaction will shift to produce more products.

Accepted Answer

The reaction will shift to produce more products.

Question 2

For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), the equilibrium constant Kp is expressed as:
Correct answer: Kp = (P_$$NH3)^2$$ / [ (P_N2)(P_$$H2)^3$$ ]

Accepted Answer

Kp = (P_$$NH3)^2$$ / [ (P_N2)(P_$$H2)^3$$ ]

Question 3

A reaction has an equilibrium constant K = $$2.5 × 10^5 at 298 K. $$What does this indicate about the reaction at equilibrium?
Correct answer: Products are heavily favored over reactants.

Accepted Answer

Products are heavily favored over reactants.

Question 4

Which of the following statements is TRUE regarding the relationship between ΔG° and K?
Correct answer: If ΔG°  1 and products are favored at equilibrium.

Accepted Answer

If ΔG°  1 and products are favored at equilibrium.

Question 5

A medical laboratory is monitoring the partial pressures of O2 and CO2 in a patient’s blood. If the partial pressure of CO2 increases, how will the equilibrium of the following reaction shift? CO2(g) + H2O(l) ⇌ H2CO3(aq)
Correct answer: The reaction will shift to the right, producing more H2CO3.

Accepted Answer

The reaction will shift to the right, producing more H2CO3.

Question 6

For the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g), the following concentrations are measured: [SO2] = 0.10 M, [O2] = 0.20 M, [SO3] = 0.50 M. If Kc = 10, what is the value of Qc and in which direction will the reaction proceed?
Correct answer: Qc = 12.5; reaction shifts left (toward reactants).

Accepted Answer

Qc = 12.5; reaction shifts left (toward reactants).

Question 7

Which of the following best describes the effect of increasing the pressure on a gaseous equilibrium system where the number of moles of gas decreases from reactants to products?
Correct answer: The equilibrium shifts toward the side with fewer moles of gas.

Accepted Answer

The equilibrium shifts toward the side with fewer moles of gas.

Question 8

Consider two reactions: (1) A ⇌ B, K1 = 4; (2) B ⇌ C, K2 = 2. What is the equilibrium constant for the overall reaction A ⇌ C?
Correct answer: K = 8

Accepted Answer

K = 8

Question 9

A student calculates Q for a reaction and finds Q \u003c K. Which of the following is the best interpretation?
Correct answer: The reaction will proceed forward to form more products.

Accepted Answer

The reaction will proceed forward to form more products.

Question 10

Which of the following is NOT a correct statement about chemical equilibrium?
Correct answer: At equilibrium, the concentrations of reactants and products are always equal.

Accepted Answer

At equilibrium, the concentrations of reactants and products are always equal.

Question 11

For the reaction: aA + bB ⇌ cC + dD, which of the following is the correct equilibrium expression for Kc?
Correct answer: Kc = ([C]^c [D]^d) / ([A]^a [B]^b)

Accepted Answer

Kc = ([C]^c [D]^d) / ([A]^a [B]^b)

Question 12

A reaction has ΔG° = +15 kJ/mol at 298 K. Which of the following statements is correct?
Correct answer: K \u003c 1 and reactants are favored at equilibrium.

Accepted Answer

K \u003c 1 and reactants are favored at equilibrium.

Question 13

In a real-world scenario, the industrial synthesis of ammonia (Haber process) is performed at high pressure. Why is this condition favorable for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)?
Correct answer: High pressure shifts equilibrium toward ammonia, which has fewer moles of gas.

Accepted Answer

High pressure shifts equilibrium toward ammonia, which has fewer moles of gas.

Question 14

If the standard free energy change (ΔG°) for a reaction is zero, what is the value of the equilibrium constant (K)?
Correct answer: K = 1

Accepted Answer

K = 1

Question 15

A solution contains 0.2 M A, 0.1 M B, 0.4 M C, and 0.5 M D for the reaction: A + B ⇌ C + D. If Kc = 10, what is the value of Qc and what does it indicate?
Correct answer: Qc = 10; the system is at equilibrium.

Accepted Answer

Qc = 10; the system is at equilibrium.

Question 16

Which of the following changes will NOT affect the value of the equilibrium constant (K) for a given reaction?
Correct answer: Adding more reactant to the system.

Accepted Answer

Adding more reactant to the system.

Question 17

For a reaction at equilibrium, which of the following is always true?
Correct answer: ΔG = 0

Accepted Answer

ΔG = 0

Question 18

A chemist combines two reactions: (1) X ⇌ Y, K1 = 0.1; (2) Y ⇌ Z, K2 = 10. What is the equilibrium constant for X ⇌ Z?
Correct answer: K = 1

Accepted Answer

K = 1

Question 19

Which of the following best explains why the equilibrium constant expression for a reaction involving only gases uses partial pressures instead of concentrations?
Correct answer: Partial pressures are directly proportional to the number of moles of gas and are more convenient to measure for gases.

Accepted Answer

Partial pressures are directly proportional to the number of moles of gas and are more convenient to measure for gases.

Chemical Equilibrium and Le Châtelier’s Principle

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