NEET · Chemistry · STD 12 - 3. Chemical kinetics

The correct difference between first- and second-order reaction is that

A the rate of a first-order reaction does not depend on reactant concentration; the rate of a secondorder reaction does depend on reactant concentrations
B the half-life of a first-order reaction does not depend on \([A]_0\); the half-life of a second-order reaction does depend on \([A]_0\)
C first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed.
D the rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations

Verified Solution

Answer & Solution

Correct Answer

(B) the half-life of a first-order reaction does not depend on \([A]_0\); the half-life of a second-order reaction does depend on \([A]_0\)

Step-by-step Solution

Detailed explanation

\(\left(\mathrm{t}_{1 / 2}\right) 1^{\mathrm{st}}\) order \(=\) Independent of Concentration \(\left(\mathrm{t}_{1 / 2}\right) 2^{\mathrm{nd}}\) order \(\propto \frac{1}{[\mathrm{A}]_{0}}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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