MCQs on Chemical Equilibrium

Everything tries to achieve minimum energy to remain stable. In a chemical reaction, reactants undergo changes to lower the energy and the reaction proceeds until a low energy state is reached. In a state of chemical equilibrium, the concentration of reactants and products doesn’t change with time and there is no observable change in the system. In a dynamic equilibrium state, the rate of the forward reaction is equal to the rate of backward reaction.

1. Find the pH of a solution when 0.01 M HCl and 0.1 M NaOH are mixed in equal volumes

(a) 12.65

(b) 1.04

(c) 7.0

(d) 2.0

Answer: (a)

2. Which of the following aqueous solution will be the best conductor of electricity?

(a) NH₃

(b) CH₃COOH

(c) HCl

(d) C₆H₁₂O₆

Answer: (c)

3. In 0.10 M aqueous solution of pyridine (C₅H₅N), find the percentage of pyridine that forms pyridinium ion (C₅H₅N⁺H) (K_b for C₅H₅N = 1.7 x 10^-9 )

(a) 1.6%

(b) 0.77%

(c) 0.0060%

(d) 0.013%

Answer: (d)

4. Find the equilibrium constant of the reaction

If the equilibrium constant for the following reactions are given

(a) K₂K₃/K₁

(b) K₁K₃³/K₂

(c) K₂K₃³/K₁

(d) K₂³K₃/K₁

Answer: (c)

5. Highest pH will be recorded for which of the following solutions if they are equimolar

(a) AlCl₃

(b) BaCl₂

(c) BeCl₂

(d) LiCl

Answer: (b)

6. The equilibrium constant is 278 for the reaction

at the same temperature, what will be the equilibrium constant for the following reaction?

(a) 6 x 10^-2

(b) 1.8 x 10^-3

(c) 1.3 x 10^-5

(d) 3.6 x 10^-5

Answer: (a)

7. What will be the pH of a buffer solution having an equal concentration of B^– and HB (K_b = 10^-10 for B^–)

(a) 7

(b) 4

(c) 10

(d) 6

Answer: (b)

8. Find the increase in equilibrium concentration of Fe³⁺ ions if OH^– ions concentration decreases to 1/4th in the following reaction

(a) 8 times

(b) 16 times

(c) 4 times

(d) 64 times

Answer: (d)

9. On increasing the concentration of reactants in a reversible reaction, then equilibrium constant will

(a) depend on the concentration

(b) increase

(c) unchanged

(d) decrease

Answer: (c)

10. Find the conjugate acid of NH₂^–

(a) NH₃

(b) NH₄OH

(c) NH₄⁺

(d) NH₂^–

Answer: (a)

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