Question

The proposed mechanism for a reaction is 1. ClO-(aq) + H2O(l) => HClO(aq) + OH-(aq) SLOW 2. I-(aq) + HClO(aq) => HIO(aq) + Cl-(aq) FAST 3. OH-(aq) + HIO(aq) => H2O(l) + IO-(aq) FAST Which of the following would be a rate law for the reaction? A. rate = k[ClO-][H2O] B. rate = k[I-][HClO] C. rate = k[OH-][HIO] D. rate = k[ClO-][H2O][I -] E. rate = k[ClO-][H2O][I-][OH-]

Answer 1

Answer:

The correct answer is option A.

Explanation:

Step 1 : Slow

$ClO^-(aq) + H_2O(l)\rightarrow HClO(aq) + OH^-(aq)$

Step 2: Fast

$I^-(aq) + HClO(aq)\rightarrow HIO(aq) + Cl^-(aq)$

Step 3: Fast

$OH^-(aq) + HIO(aq)\rightarrow H_2O(l) + IO^-(aq)$

When there is a recation which is taking place in a more that single steps than  the rate of the reaction is determined by the slowest step occurring in the reaction mechanism.

So, according to question step 1 is slow step which means that rate of the reaction will be :

$R=k[ClO^-][H_2O]$