AQA GCSE Chemistry

Revision Notes

6.2.6 The Effect of Temperature Changes on Equilibrium

Higher Tier Only

The Effect of Temperature Changes on Equilibrium

  • Le Chatelier’s Principle can be used to predict the effect of changes in temperature on systems in equilibrium
  • To make this prediction it is necessary to know whether the reaction is exothermic or endothermic
  • The following table summarises how a temperature change alters the position of equilibrium:

Effect of Temperature Changes on an Equilibrium Table

Effect of Temperature on Equilibrium, downloadable IGCSE & GCSE Chemistry revision notes

Worked Example

Iodine monochloride reacts reversibly with chlorine to form iodine trichloride:

2ICl (l) + Cl2 (g) ⇌ ICl3 (s)

dark brown            yellow

When the equilibrium mixture is heated, it becomes dark brown in colour. Explain whether the backward reaction is exothermic or endothermic.

Answer

    • The equilibirum has shifted to the left as the dark brown colour means that more of the ICl is produced. Increasing the temperature moves the equilbrium in the endothermic direction, so the reverse reaction is endothermic

Exam Tip

Remember all reversible reactions are exothermic in one direction and endothermic in the other.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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