250+ TOP MCQs on Relationship between Equilibrium Constant K, Reaction Quotient Q and Gibbs Energy G and Answers

Chemistry Multiple Choice Questions and Answers for Class 11 on “Relationship between Equilibrium Constant K, Reaction Quotient Q and Gibbs Energy G”.

1. In a reaction, at 300k, K_C is given as 2 x 10¹³, then what is the value of ΔG?
a) – 7.64 × 10⁴ J
b) – 7.64 × 10⁴ J mol^–1
c) – 7.64 × 10 J mol^–1
d) – 7.64 × 10⁴ mol^–1
Answer: b
Clarification: We know that ΔG₀ = – RT lnK_c, where ΔG₀ is the standard Gibbs free energy, R is universal gas constant, T is the temperature and K_C is equilibrium constant; substituting K_C as 2 x 10¹³, ΔG₀ = (– 8.314J mol^–1K^–1 × 300K) × ln(2×10¹³); ΔG₀ = – 7.64 × 10⁴ J mol^–1.

2. For a chemical reaction, the value of ΔG₀ is -831.4 J/mol. Then what is the value of K_C at 100 k?
a) 1.0077
b) 1.077
c) 1.007
d) 2.7
Answer: d
Clarification: We know that ΔG₀ = – RT lnK_c, where ΔG₀ is the standard Gibbs free energy, R is universal gas constant, T is the temperature and K_C is equilibrium constant; substituting ΔG₀ as -831.4 J/mol, we get lnk = -831.4J/mol divided by -8.314J mol^–1K^–1 × 100K = 1; lnk = 1; K = e¹ = 2.7

3. If the value of ΔG₀ is -2502 J/mol and K is 2, what is the temperature of the reaction that is occurring?
a) 200 k
b) 101 k
c) 100 k
d) 300 k
Answer: c
Clarification: We know that ΔG₀ = – RT lnK_c, where ΔG₀ is the standard Gibbs free energy, R is universal gas constant, T is the temperature and K_C is equilibrium constant; substituting ΔG₀ as -2502 J/mol, we get -2502 J/mol = -8.314J mol^–1K^–1 × T ln2 = 2502 J/mol = T = 2502/2.502 = 100 k.

4. In a reaction, if the value of Gibbs free energy is greater than zero what does it infer?
a) K is greater than 1
b) K is less than 1
c) K is equal to 1
d) Cannot deduce K from Gibbs free energy
Answer: b
Clarification: If the value of Gibbs free energy is greater than the zero that means, -ΔG₀/RT is negative and that e^-ΔG₀/RT is greater than 1, so the K is greater than 1 this means the reaction is nonspontaneous and proceeds in the forward direction.

5. When is a reaction nonspontaneous?
a) Gibbs free energy is positive
b) Gibbs free energy is negative
c) Gibbs free energy is zero
d) Does not depend on Gibbs free energy
Answer: a
Clarification: When Gibbs free energy is positive, the reaction that occurs is nonspontaneous and a reaction occurs backward that is the products are converted into reactants. Simply the reverse reaction could occur.

6. What did the Q depicted in the equation; ΔG = ΔG₀ + RT lnQ?
a) reaction coefficient
b) reaction quotient
c) equilibrium constant
d) free energy
Answer: b
Clarification: In the equation ΔG = ΔG₀ + RT lnQ, ΔG is the Gibbs free energy, R is the universal gas constant, T is the temperature and Q is the reaction quotient. When Gibbs free energy is zero, the reaction quotient becomes equilibrium constant.

7. If the value of Gibbs free energy for a reaction is 20J/mol, the reaction is ___________
a) spontaneous
b) nonspontaneous
c) may be spontaneous
d) may not be spontaneous
Answer: b
Clarification: Is the value of Gibbs free energy for a reaction is 20 J/mol, that means it is positive, -ΔG₀/RT is negative and that e^-ΔG₀/RT is greater than 1, so the K is greater than 1 this means the reaction is nonspontaneous.

8. For a reaction, K_c = 3.81 × 10^–3 and ΔG₀ = 13.8 kJ/mol. Then what is the value of R?
a) -8.314J mol^–1K^–1
b) 8.314J mol^–1K^–1
c) cannot say as the temperature is not given
d) -8.314J mol^–1
Answer: b
Clarification: Though the temperature is not given, universal gas constant value always remains the same, whatever may be the other values. So the universal gas constant is given by a constant value that is -8.314J mol^–1K^–1.

9. What happens when reaction quotient is equal to the equilibrium constant?
a) the reaction proceeds in the forward direction
b) the reaction proceeds in the backward direction
c) the reaction reaches equilibrium
d) cannot predict
Answer: c
Clarification: When Gibbs free energy is zero, the reaction reaches equilibrium and at equilibrium, the reaction quotient is replaced by the equilibrium constant, as both the values are equal. That is when reaction quotient is equal to the equilibrium constant reaction reaches equilibrium.

10. Is a relationship between reaction quotient and Gibbs free energy at a temperature T?
a) ΔG = ΔG₀ + RT lnQ
b) ΔG = ΔG₀ + RT lnk
c) ΔG = ΔG₀ + R lnQ
d) ΔD = ΔG₀ + RT lnQ
Answer: a
Clarification: The relationship between reaction quotient and Gibbs free energy at temperature t is given as as ΔG = ΔG₀ + RT lnQ, where ΔG is the Gibbs free energy, R is the universal gas constant, T is the temperature and Q is the reaction quotient.

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