The decomposition of hydrogen peroxide is given by the following reaction:2 H2O2 (aq) → 2 H2O (l) + O2 (g) In the presence of KI the reaction is thought to occur by the following mechanism:Step 1: H2O2 + I - → H2O + IO-Step 2: IO - + H2O2 → H2O + O2 + I-What is the role of I - in this mechanism?

Question

Leyla

Chemistry

25 June, 00:33

The decomposition of hydrogen peroxide is given by the following reaction:2 H2O2 (aq) → 2 H2O (l) + O2 (g) In the presence of KI the reaction is thought to occur by the following mechanism:Step 1: H2O2 + I - → H2O + IO-Step 2: IO - + H2O2 → H2O + O2 + I-What is the role of I - in this mechanism?

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Tanner Noble · Answer 1

Role of I⁻ in this mechanism is a catalyst

Explanation:

The decomposition of hydrogen peroxide is catalyzed as shown below.

The catalyzed reaction is thought to proceed by a two-step mechanism:

H₂O₂ + I⁻ → H₂O + IO⁻ (slow)

IO⁻ + H₂O₂ → I⁻ + H₂O + H₂O₂ (fast)

The rate law for the overall process Rate=k [H₂O₂][I⁻ ] according to slow elementary step. However, it's not consumed in the reaction and therefore changing its concentration does not impact rate. Its behavior as a catalyst will impact the value for k. This is often designated with k' so we can write the rate law as: Rate=k' [H₂O₂]