Question

Identify correct statement regarding order of reaction from following.

• A. Rate of zero order reaction depends on initial concentration of reactant.
• B. Decomposition of acetaldehyde is a first order reaction.
• C. Half life of first order reaction is independent of initial concentration of reactant.
• D. Half life of zero order reaction is independent of initial concentration of reactant

Hint:

Half-life of a first-order reaction does not depend on initial concentration.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The half-life of a reaction depends on its order. For a first-order reaction it is a constant, while for other orders it changes with the starting concentration.

Step 2: Key Formulas:
First order: \(t_{1/2} = \dfrac{0.693}{k}\), independent of \([A]_0\).
Zero order: \(t_{1/2} = \dfrac{[A]_0}{2k}\), proportional to \([A]_0\).

Step 3: Detailed Explanation:
Statement (C) says the half-life of a first-order reaction does not depend on the initial concentration. This agrees with \(t_{1/2} = 0.693/k\), which contains only the rate constant. So (C) is correct.

Step 4: Why the other options are wrong.
(A) is false: for a zero order reaction the rate equals \(k\) and does not depend on concentration of reactant. (B) is false: decomposition of acetaldehyde follows a fractional (3/2) order, not first. (D) is false: zero order half-life is \([A]_0/2k\), directly proportional to the initial concentration.

Final Answer:
Statement (C) is correct. \[ \boxed{\text{(C)}} \]