The Effect of Temperature Changes on Equilibrium (AQA GCSE Chemistry)
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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
Worked example
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
Exam Tip
Remember all reversible reactions are exothermic in one direction and endothermic in the other.
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