A student sets up a reversible reaction in a closed container and allows it to reach equilibrium. The student then increases the temperature. Explain how increasing the temperature affects the position of equilibrium and the value of the equilibrium constant, Kp, for an endothermic forward reaction.

AQA A-Level Chemistry (7405) — 3.1.10 Equilibrium constant Kp (A-Level only) · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Increasing the temperature shifts the equilibrium to the endothermic side. The system absorbs the added heat, so more reactants are converted to products and the yield of products increases. Consequently the equilibrium constant Kp, which depends only on temperature, increases.

Examiner tips

  • Use the word ‘shifts’ to show direction change; mention absorption of heat; state that more products are formed; note Kp rises; remember Kp is temperature‑dependent only.
  • Include the key terms: endothermic, equilibrium position, Kp, temperature dependence.

Common mistakes

  • Saying the equilibrium shifts to the exothermic side; confusing Kp with Kc; ignoring that Kp changes only with temperature, not pressure or concentration.

Mark scheme (5 marks)

  1. Increasing temperature shifts the position of equilibrium in the direction of the endothermic reaction
  2. This is because the system absorbs the extra energy/heat added
  3. More products are formed (and less reactants remain) / yield of products increases
  4. The value of Kp increases
  5. Because Kp depends only on temperature, not on pressure or concentration

Key terms in this question

position of equilibrium · endothermic · reversible reaction

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