Question

The decomposition of \(H_{2}O_{2}\) in the presence of \(I^{-}\) in alkaline medium has the rate law.

• A. $-d[H_{2}O_{2}]/dt=k[H_{2}O_{2}]$
• B. $-d[H_{2}O_{2}]/dt=k[H_{2}O_{2}][OH^{-}]$
• C. $-d[H_{2}O_{2}]/dt=k[H_{2}O_{2}][I^{-}]$
• D. $-d[H_{2}O_{2}]/dt=k[H_{2}O_{2}]^{1/2}[I^{-}]$
• E. $-d[H_{2}O_{2}]/dt=k[H_{2}O_{2}][I^{-}]^{1/2}$

Hint:

In catalyzed reactions, the concentration of the catalyst often appears in the rate law.

Answer 1

The Correct Option is C

Step 1: Concept
The decomposition of hydrogen peroxide catalyzed by iodide ion is a first-order reaction with respect to both $H_{2}O_{2}$ and the catalyst $I^{-}$.

Step 2: Meaning
The rate of reaction depends linearly on the concentration of the reactant and the concentration of the catalyst used.

Step 3: Analysis
Experimental data for this specific catalytic decomposition shows that the overall order of the reaction is 2, being first order in each species.

Step 4: Conclusion
Hence, the rate law is rate $= k[H_{2}O_{2}][I^{-}]$.
Final Answer: (C)