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AS & A Level · AS/A Level

Chemistry

Equilibria, acids and buffers

Name: ____________________Date: October 10, 2026
  1. 1.

    Explain what is dynamic about equilibrium in a closed reversible reaction.

    [3 marks] · no calculator
  2. 2.

    Distinguish a weak acid from a dilute acid, and explain whether dilution changes an acid's intrinsic strength at fixed temperature.

    [3 marks] · no calculator
  3. 3.

    At equilibrium for H2 + I2 <=> 2HI, [H2] = 0.20, [I2] = 0.10 and [HI] = 0.40 mol dm^-3. Calculate Kc.

    [3 marks]
  4. 4.

    Calculate the pH of 0.0200 mol dm^-3 HCl, assuming complete dissociation and negligible water contribution.

    [3 marks]
  5. 5.

    A buffer contains HA and A^-. Explain separately how it resists added H+ and added OH-, and why a large addition can overwhelm it.

    [4 marks] · no calculator
  6. 6.

    N2 + 3H2 <=> 2NH3 is exothermic. Evaluate increasing pressure and decreasing temperature to maximise industrial production, separating equilibrium yield from rate and operating cost.

    [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.

Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.