Chemistry Equilibrium Test

Multiple Choice Questions (MCQs)

1. In a homogeneous equilibrium, all reactants and products are:
   • (A) In different phases
   • (B) In the same phase
   • (C) Either in liquid or solid phase
   • (D) Either in solid or gaseous phase
2. Which of the following statements is correct regarding a heterogeneous equilibrium?
   • (A) The concentration of solids and liquids is included in the equilibrium expression
   • (B) Only gases are considered when writing the equilibrium constant expression
   • (C) Solids are ignored, but liquids are included in the equilibrium constant expression
   • (D) Solids and liquids are both ignored when writing the equilibrium constant expression
3. The equilibrium constant K_c for a reaction is expressed in terms of:
   • (A) Partial pressures of reactants and products
   • (B) Concentrations of reactants and products
   • (C) Number of moles of reactants and products
   • (D) Temperature of the reaction
4. For the reaction N₂(g) + 3H₂(g) ↔ 2NH₃(g), the expression for K_p in terms of K_c is:
   • (A) K_p = K_c(RT)²
   • (B) K_p = K_c(RT)³
   • (C) K_p = K_c(RT)^-1
   • (D) K_p = K_c(RT)^-2
5. In a reaction where K_p > K_c, we can conclude that:
   • (A) There are more reactants than products at equilibrium
   • (B) The reaction is at equilibrium under high pressure
   • (C) The number of moles of gaseous products is greater than that of gaseous reactants
   • (D) The number of moles of gaseous reactants is greater than that of gaseous products

Assertion-Reason Questions

For each of the following questions, choose:

• (A) If both assertion and reason are correct, and the reason is the correct explanation of the assertion
• (B) If both assertion and reason are correct, but the reason is not the correct explanation of the assertion
• (C) If the assertion is correct, but the reason is incorrect
• (D) If both the assertion and reason are incorrect

6. Assertion: In the equilibrium expression for a reaction involving a solid, the concentration of the solid is not included.
   Reason: Solids have a fixed concentration due to their constant density, which does not change during the reaction.
7. Assertion: For a reaction where the number of moles of gas changes, K_p and K_c will have different values.
   Reason: K_p and K_c differ by a factor that depends on the number of moles of gaseous reactants and products and the temperature.
8. Assertion: In a heterogeneous equilibrium involving gases and solids, only the gaseous components are included in the equilibrium constant expression.
   Reason: The concentration of solids remains constant and thus does not affect the equilibrium state.
9. Assertion: If K_p = K_c, then the number of moles of gaseous reactants is equal to that of gaseous products.
   Reason: K_p and K_c are related through the equation K_p = K_c(RT)^Δn, where Δn = 0 when moles of reactants equal moles of products.
10. Assertion: For the reaction CO(g) + H₂O(g) ↔ CO₂(g) + H₂(g), the equilibrium constant is unaffected by changes in the concentration of solids present.
    Reason: This reaction only involves gases, so the presence or absence of solids does not impact K_c or K_p.

One-Word Answer Questions

11. In a chemical equilibrium expression, which state of matter is not included for any substance?
12. If Δn for a reaction is zero, what is the relation between K_p and K_c?
13. What do we call the equilibrium constant that is expressed in terms of the partial pressures of gases?
14. In the equilibrium reaction CaCO₃(s) ↔ CaO(s) + CO₂(g), which component(s) would be included in the expression for K_p?
15. For the reaction 2NO(g) + O₂(g) ↔ 2NO₂(g), if K_p = 1.5 × 10³ at a certain temperature, what is the equilibrium constant for the reverse reaction?

Answers for Chemistry Equilibrium Test

Multiple Choice Questions (MCQs)

1. (B)
2. (D)
3. (B)
4. (A)
5. (D)

Assertion-Reason Questions

6. (A)
7. (A)
8. (A)
9. (A)
10. (B)

One-Word Answer Questions

11. Solid
12. K_p = K_c
13. K_p
14. CO₂(g)
15. 6.67 × 10^-4

HW QUESTIONS

Equilibrium – 2 Marker Questions and Numericals

2-Mark Questions

1. Define homogeneous and heterogeneous equilibrium with one example each.
2. Explain why solids and liquids are not included in the expression for equilibrium constant, K_c.
3. Differentiate between K_c and K_p with respect to chemical equilibrium.
4. State the Law of Chemical Equilibrium and write the expression for the equilibrium constant for the reaction:
   aA + bB ↔ cC + dD.
5. If the equilibrium constant K_c for a reaction is very large, what does it imply about the extent of the reaction? Explain.

Numerical Problems

1. For the reaction
   H₂(g) + I₂(g) ↔ 2HI(g),
   the equilibrium concentrations at 700 K are: [H₂] = 0.2 mol/L, [I₂] = 0.1 mol/L, and [HI] = 1.2 mol/L. Calculate K_c for the reaction.
2. At a certain temperature, the equilibrium constant K_p for the reaction
   N₂O₄(g) ↔ 2NO₂(g)
   is 0.113. If the partial pressure of N₂O₄ at equilibrium is 0.5 atm, calculate the partial pressure of NO₂ at equilibrium.
3. The equilibrium constant K_p for the reaction
   SO₂(g) + (1/2)O₂(g) ↔ SO₃(g)
   is 4.34 at 300 K. Calculate K_c for this reaction at the same temperature. (Given R = 0.0821 L atm K^-1 mol^-1).
4. For the reaction
   CO(g) + 3H₂(g) ↔ CH₄(g) + H₂O(g),
   the equilibrium constant K_c is 0.18 at a certain temperature. If the initial concentration of CO is 0.2 mol/L and H₂ is 0.3 mol/L, calculate the equilibrium concentrations of CH₄ and H₂O if they start at zero concentration.
5. A reaction has an equilibrium constant K_c = 1.6 × 10³ at 500 K. If the initial concentration of the reactant is 0.5 mol/L, calculate the equilibrium concentration of the product if it starts from zero concentration. Assume the reaction is:
   A ↔ B.