Question

Which of the following is not a first order reaction?

• A. \( \text{CH}_3\text{COOCH}_3 + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{CH}_3\text{COOH} + \text{CH}_3\text{OH} \)
• B. \( \text{CH}_3\text{COOC}_2\text{H}_5 + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{C}_2\text{H}_5\text{OH} \)
• C. \( 2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2 \)
• D. \( 2\text{N}_2\text{O}_5 \rightarrow 4\text{NO}_2 + \text{O}_2 \)

Hint:

To identify reaction orders, always check the rate law. For first-order reactions, the rate depends linearly on the concentration of one reactant.

Answer 1

The Correct Option is D

Step 1: Analyzing the reactions.
To determine which reaction is not first order, we need to check the type of reaction for each option. A first-order reaction depends on the concentration of one reactant. Step 2: Analysis of options.
(A) The reaction \( \text{CH}_3\text{COOCH}_3 + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{CH}_3\text{COOH} + \text{CH}_3\text{OH} \) is an ester hydrolysis reaction, which is typically a first-order reaction with respect to the ester.
(B) The reaction \( \text{CH}_3\text{COOC}_2\text{H}_5 + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{C}_2\text{H}_5\text{OH} \) is an example of ester hydrolysis, also a first-order reaction.
(C) The reaction \( 2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2 \) is the decomposition of hydrogen peroxide, which is a first-order reaction.
(D) The reaction \( 2\text{N}_2\text{O}_5 \rightarrow 4\text{NO}_2 + \text{O}_2 \) is a second-order reaction, not a first-order reaction. This is a decomposition reaction that involves a different reaction order.
Step 3: Conclusion.
The correct answer is (D), as it is not a first-order reaction.