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 equilibrium constant expression in terms of concentration?
A.
Kc = [HI]² / ([H2][I2])
B.
Kc = [H2][I2] / [HI]²
C.
Kc = [HI] / ([H2][I2])
D.
Kc = [H2]²[I2]² / [HI]
Correct Answer:
Kc = [HI]² / ([H2][I2])
Explanation:
The concentrations of products are written 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 = [N2][H2]³ / [NH3]²
B.
Kc = [NH3]² / ([N2][H2]³)
C.
Kc = [NH3] / ([N2][H2])
D.
Kc = [NH3]³ / ([N2]²[H2])
Correct Answer:
Kc = [NH3]² / ([N2][H2]³)
Explanation:
The equilibrium constant expression has product concentration in the numerator and reactant concentrations in the denominator, with powers equal to their coefficients.
3. For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), what is the correct Kc expression?
A.
Kc = [SO2]²[O2] / [SO3]²
B.
Kc = [SO3]² / ([SO2]²[O2])
C.
Kc = [SO3] / ([SO2][O2])
D.
Kc = [SO2][O2]² / [SO3]
Correct Answer:
Kc = [SO3]² / ([SO2]²[O2])
Explanation:
The coefficient 2 for SO3 becomes its exponent, while the coefficients 2 and 1 for SO2 and O2 become their exponents in the denominator.
4. For the heterogeneous equilibrium CaCO3(s) ⇌ CaO(s) + CO2(g), which species appears in the Kc expression?
A.
CaCO3(s) only
B.
CaO(s) only
C.
CO2(g) only
D.
CaCO3(s) and CaO(s)
Correct Answer:
CO2(g) only
Explanation:
The concentrations of pure solids are constant and are not included in the equilibrium constant expression. Therefore, Kc = [CO2].
5. For the reaction H2(g) + Cl2(g) ⇌ 2HCl(g), which is the correct expression for Kp?
A.
Kp = (PHCl)² / (PH2 PCl2)
B.
Kp = (PH2 PCl2) / (PHCl)²
C.
Kp = PHCl / (PH2 PCl2)
D.
Kp = (PHCl)²PH2PCl2
Correct Answer:
Kp = (PHCl)² / (PH2 PCl2)
Explanation:
For Kp, partial pressures of gaseous products are placed over partial pressures of gaseous reactants, and each is raised to its stoichiometric coefficient.
6. For the reaction PCl5(g) ⇌ PCl3(g) + Cl2(g), which is the correct Kc expression?
A.
Kc = [PCl5] / ([PCl3][Cl2])
B.
Kc = [PCl3][Cl2] / [PCl5]
C.
Kc = [PCl3] / ([PCl5][Cl2])
D.
Kc = [PCl5][Cl2] / [PCl3]
Correct Answer:
Kc = [PCl3][Cl2] / [PCl5]
Explanation:
The products PCl3 and Cl2 are written in the numerator, while the reactant PCl5 is written in the denominator.
7. For the equilibrium 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 with coefficient 2. Thus, Kc = [N2O4]/[NO2]².
8. In an equilibrium constant expression, the concentration of a pure liquid is generally:
A.
Included with an exponent equal to its coefficient
B.
Included only if it is a product
C.
Omitted because its concentration is constant
D.
Placed in the denominator in every case
Correct Answer:
Omitted because its concentration is constant
Explanation:
Pure liquids, like pure solids, have constant concentrations and are not included in equilibrium constant expressions.
9. For the reaction CO(g) + H2O(g) ⇌ CO2(g) + H2(g), what is the correct Kc 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:
The products CO2 and H2 are in the numerator, and the reactants CO and H2O are in the denominator. All coefficients are 1, so no powers greater than 1 are needed.
10. For the reaction 2SO3(g) ⇌ 2SO2(g) + O2(g), which is the correct Kp expression?
A.
Kp = (PSO3)² / ((PSO2)²PO2)
B.
Kp = (PSO2)²PO2 / (PSO3)²
C.
Kp = PSO2PO2 / (PSO3)²
D.
Kp = (PSO2)² / (PSO3PO2)
Correct Answer:
Kp = (PSO2)²PO2 / (PSO3)²
Explanation:
For Kp, the partial pressures of gaseous products are in the numerator and those of gaseous reactants are in the denominator, raised to their stoichiometric coefficients.