Question

Which of the following is a pseudo-first order reaction?

• A. Decomposition of ammonia on platinum metal
• B. Decomposition of \(\text{H}_{2}\text{O}_{2}(l)\)
• C. Decomposition of \(\text{N}_{2}\text{O}_{5}(g)\)
• D. Hydrolysis of methyl acetate

Hint:

A pseudo first order reaction is a higher order reaction that behaves as first order because one reactant is in large excess.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
A pseudo first order reaction is truly bimolecular or of higher order, but one reactant is present in such large excess that its concentration stays almost constant.

Step 2: Examine the options
Decomposition of ammonia on platinum is zero order, and decomposition of \(\text{H}_{2}\text{O}_{2}\) and \(\text{N}_{2}\text{O}_{5}\) are genuinely first order.

Step 3: Hydrolysis of methyl acetate
\(\text{CH}_3\text{COOCH}_3+\text{H}_2\text{O}\rightarrow\text{CH}_3\text{COOH}+\text{CH}_3\text{OH}\)
Water is in large excess, so the rate depends only on the ester concentration.

Final Answer:
Hydrolysis of methyl acetate is the pseudo first order reaction. \[ \boxed{\text{(D) }\text{Hydrolysis of methyl acetate}} \]