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Iodide ions are oxidised to iodine by hydrogen peroxide in acidic conditions - AQA - A-Level Chemistry - Question 1 - 2018 - Paper 3
Question 1
Iodide ions are oxidised to iodine by hydrogen peroxide in acidic conditions. $$\text{H}_2\text{O}_2(aq) + 2\text{H}^+(aq) + 2\text{I}^-(aq) \rightarrow \text{I}_2(... show full transcript
Worked Solution & Example Answer:Iodide ions are oxidised to iodine by hydrogen peroxide in acidic conditions - AQA - A-Level Chemistry - Question 1 - 2018 - Paper 3
Step 1
Explain why the use of a large excess of H2O2 and I− means that the rate of reaction at a fixed temperature depends only on the concentration of H+(aq).
Answer
The presence of a large excess of H2O2 and I− ensures that their concentrations remain effectively constant throughout the reaction. This means that any changes in the rate of reaction can be attributed solely to variations in the concentration of H+(aq).
Since the concentration of H2O2 and I− does not change significantly, they do not affect the rate, which simplifies the rate equation to depend only on [H+]. Thus, the order of the reaction with respect to H+ can be determined without interference from the other reactants.