The Effect of Temperature Changes on Equilibrium (AQA GCSE Chemistry)

Iodine monochloride reacts reversibly with chlorine to form iodine trichloride and the forward reaction is exothermic:

ICl (l) + Cl₂ (g) ⇌ ICl₃ (s)

dark brown            yellow

What colour will the mixture turn when heated? Explain your answer.

Answer:

• When a system is heated, the system opposes the change by doing more of the endothermic reaction
• Since the forward reaction is exothermic, the backward reaction is endothermic
• Therefore the equilibrium will move to the left and produce more of the reactants
• The colour of the mixture will become increasingly brown as more ICl is produced