chemistry : class11 Equilibrium Constant Expressions : Equilibrium in chemical processes : Equilibrium MCQ Questions and Answers
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Equilibrium Constant Expressions
MCQ questions and answers.
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MCQ Questions
1. For the reaction H2(g) + I2(g) ⇌ 2HI(g), what is the correct equilibrium constant expression in terms of concentration?
A.
Kc = [HI] / ([H2][I2])
B.
Kc = [HI]^2 / ([H2][I2])
C.
Kc = [H2][I2] / [HI]^2
D.
Kc = [H2][I2] / [HI]
Correct Answer:
Kc = [HI]^2 / ([H2][I2])
Explanation:
The concentrations of products are placed in the numerator and those of reactants in the denominator. Each concentration is raised to the power of its stoichiometric coefficient.
2. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), which is the correct expression for Kc?
A.
Kc = [NH3]^2 / ([N2][H2]^3)
B.
Kc = [N2][H2]^3 / [NH3]^2
C.
Kc = [NH3] / ([N2][H2])
D.
Kc = [NH3]^3 / ([N2][H2]^2)
Correct Answer:
Kc = [NH3]^2 / ([N2][H2]^3)
Explanation:
The product NH3 has coefficient 2, while N2 and H2 have coefficients 1 and 3. These coefficients become the powers in the equilibrium constant expression.
3. For the reaction CaCO3(s) ⇌ CaO(s) + CO2(g), what is the correct expression for Kc?
A.
Kc = [CaO][CO2] / [CaCO3]
B.
Kc = [CO2]
C.
Kc = [CaCO3] / [CO2]
D.
Kc = [CaO][CO2]
Correct Answer:
Kc = [CO2]
Explanation:
Pure solids such as CaCO3 and CaO are not included in the equilibrium constant expression. Only the gaseous CO2 appears.
4. For the reaction H2O(l) ⇌ H+(aq) + OH−(aq), which is the correct expression for Kc?
A.
Kc = [H2O] / ([H+][OH−])
B.
Kc = [H+][OH−]
C.
Kc = [H+][OH−][H2O]
D.
Kc = [H2O]
Correct Answer:
Kc = [H+][OH−]
Explanation:
Pure liquid water is omitted from the equilibrium constant expression because its concentration is effectively constant. The aqueous ions are included.
5. For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), what is the correct expression for Kc?
A.
Kc = [SO3]^2 / ([SO2]^2[O2])
B.
Kc = [SO3] / ([SO2][O2])
C.
Kc = [SO2]^2[O2] / [SO3]^2
D.
Kc = [SO3]^2 / ([SO2][O2]^2)
Correct Answer:
Kc = [SO3]^2 / ([SO2]^2[O2])
Explanation:
The coefficients in the balanced equation become exponents. SO3 and SO2 have coefficient 2, while O2 has coefficient 1.
6. For the equilibrium reaction 2NO2(g) ⇌ N2O4(g), which expression represents Kc?
A.
Kc = [NO2]^2 / [N2O4]
B.
Kc = [N2O4] / [NO2]^2
C.
Kc = [N2O4]^2 / [NO2]
D.
Kc = [NO2] / [N2O4]^2
Correct Answer:
Kc = [N2O4] / [NO2]^2
Explanation:
N2O4 is the product and has coefficient 1, while NO2 is the reactant and has coefficient 2. Therefore, Kc equals [N2O4] divided by [NO2]^2.
7. For the reaction CO(g) + H2O(g) ⇌ CO2(g) + H2(g), what is the correct equilibrium constant expression?
A.
Kc = [CO][H2O] / ([CO2][H2])
B.
Kc = [CO2][H2] / ([CO][H2O])
C.
Kc = [CO2] / ([CO][H2O][H2])
D.
Kc = [CO][H2] / ([CO2][H2O])
Correct Answer:
Kc = [CO2][H2] / ([CO][H2O])
Explanation:
All species are included because they are gases. Products are placed in the numerator and reactants in the denominator.
8. In an equilibrium constant expression, what determines the powers applied to the concentrations?
A.
The atomic masses of the substances
B.
The stoichiometric coefficients in the balanced chemical equation
C.
The physical states of the substances only
D.
The initial concentrations of the substances
Correct Answer:
The stoichiometric coefficients in the balanced chemical equation
Explanation:
The coefficients of the balanced chemical equation become the exponents of the corresponding concentration terms in the equilibrium constant expression.
9. For the reaction 2KClO3(s) ⇌ 2KCl(s) + 3O2(g), which species appears in the Kc expression?
A.
KClO3 only
B.
KCl only
C.
O2 only
D.
KClO3 and KCl
Correct Answer:
O2 only
Explanation:
KClO3 and KCl are pure solids and are omitted. The gaseous product O2 is included, with its concentration raised to the power 3.
10. For the reaction A(g) ⇌ 2B(g), which is the correct equilibrium constant expression?
A.
Kc = [A] / [B]^2
B.
Kc = [B]^2 / [A]
C.
Kc = [B] / [A]^2
D.
Kc = [A][B]^2
Correct Answer:
Kc = [B]^2 / [A]
Explanation:
B is the product with coefficient 2, so its concentration is squared. A is the reactant with coefficient 1 and appears in the denominator.