FSc Part 1 Chemistry chapter 8: Chemical equilibrium MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

29 exam-style questions on Chemical equilibrium, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

29 questions · 3 topics · 10 per test

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What chapter 8 covers

Ten Chemical equilibrium questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. For H2(g) + I2(g) ⇌ 2HI(g), the equilibrium concentrations are [H2] = 0.10, [I2] = 0.10 and [HI] = 0.70 mol dm−3. What is Kc?

  1. A
    7.0
  2. B
    49
  3. C
    70
  4. D
    0.020
Show answer

Answer: B. Kc = [HI]2 ÷ ([H2][I2]) = 0.49 ÷ 0.010 = 49. Forgetting to square [HI] gives 70.

2. The solubility of PbCl2 is 1.6 × 10−2 mol dm−3. What is its Ksp?

  1. A
    4.1 × 10−6 mol3 dm−9
  2. B
    2.6 × 10−4 mol3 dm−9
  3. C
    1.0 × 10−3 mol3 dm−9
  4. D
    1.6 × 10−5 mol3 dm−9
Show answer

Answer: D. PbCl2 ⇌ Pb2+ + 2Cl−, so [Pb2+] = s and [Cl−] = 2s. Ksp = s(2s)2 = 4s3 = 4 × (0.016)3 = 1.6 × 10−5. Forgetting the 2 gives s3 = 4.1 × 10−6.

3. For N2O4(g) ⇌ 2NO2(g) at 298 K, Kc = 4.6 × 10−3 mol dm−3. What is Kp? (R = 0.0821 dm3 atm K−1 mol−1)

  1. A
    0.113 atm
  2. B
    1.88 × 10−4 atm
  3. C
    4.6 × 10−3 atm
  4. D
    3.78 × 10−4 atm
Show answer

Answer: A. Δn = 2 − 1 = +1, so Kp = KcRT = 4.6 × 10−3 × 0.0821 × 298 = 0.113 atm. Dividing by RT gives 1.88 × 10−4.

4. For which equilibrium is Kp equal to Kc?

  1. A
    N2 + 3H2 ⇌ 2NH3
  2. B
    PCl5 ⇌ PCl3 + Cl2
  3. C
    2SO2 + O2 ⇌ 2SO3
  4. D
    H2 + I2 ⇌ 2HI
Show answer

Answer: D. Kp = Kc(RT)Δn. For H2 + I2 ⇌ 2HI, Δn = 2 − 2 = 0, so (RT)0 = 1 and Kp = Kc.

5. Which statement describes a system at chemical equilibrium?

  1. A
    the forward and reverse reactions have both stopped
  2. B
    the concentrations of reactants and products are equal
  3. C
    the forward and reverse reactions continue at equal rates, so concentrations stay constant
  4. D
    only the forward reaction continues
Show answer

Answer: C. Equilibrium is dynamic: both reactions keep going at the same rate, so there is no net change. The concentrations are constant but usually not equal.

6. For H2(g) + I2(g) ⇌ 2HI(g), what is the effect of doubling the total pressure on the amount of HI at equilibrium?

  1. A
    it doubles
  2. B
    it is halved
  3. C
    it does not change
  4. D
    it increases four times
Show answer

Answer: C. There are 2 mol of gas on each side, so a change in pressure favours neither side.

7. 1.0 mol of ethanoic acid and 1.0 mol of ethanol are mixed. For CH3COOH + C2H5OH ⇌ CH3COOC2H5 + H2O, Kc = 4.0. How many moles of ester are present at equilibrium?

  1. A
    0.50 mol
  2. B
    0.67 mol
  3. C
    0.80 mol
  4. D
    0.33 mol
Show answer

Answer: B. x2 ÷ (1 − x)2 = 4, so x ÷ (1 − x) = 2 and x = 2/3 = 0.67 mol. Forgetting to take the square root gives 0.80.

8. What is the pH of 0.001 mol dm−3 NaOH solution at 25 °C?

  1. A
    3
  2. B
    10
  3. C
    11
  4. D
    12
Show answer

Answer: C. [OH−] = 10−3, so pOH = 3 and pH = 14 − 3 = 11. Answering 3 gives the pOH, not the pH.

9. What is the Kc expression for N2(g) + 3H2(g) ⇌ 2NH3(g)?

  1. A
    [NH3]2 ÷ ([N2][H2]3)
  2. B
    [NH3] ÷ ([N2][H2])
  3. C
    2[NH3] ÷ ([N2] × 3[H2])
  4. D
    ([N2][H2]3) ÷ [NH3]2
Show answer

Answer: A. By the law of mass action, Kc = products over reactants, each concentration raised to the power of its coefficient in the balanced equation.

10. The equilibrium constant Kn is expressed in terms of

  1. A
    mole fractions
  2. B
    partial pressures
  3. C
    molar concentrations
  4. D
    numbers of moles at equilibrium
Show answer

Answer: D. Kc uses concentrations, Kp partial pressures, Kx mole fractions and Kn numbers of moles.

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Ways to practise this chapter

Chemical equilibrium: questions students ask

How many Chemical equilibrium MCQs are there?

29, each with the answer and a short explanation, across 3 topics: Law of mass action, Kc and Kp, Le Chatelier's principle and industrial applications, Ionic equilibria: pH, buffers and solubility product. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Chemistry chapter 8 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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