NEET UG 2018 — Chemistry Physical Chemistry

2018mcqmedium

What is the correct difference between first and second order reactions?

Official previous-year question

Held on 30 Apr 2018 · Verified 9 Jul 2026.

Options

A
A first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed.
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
The rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations.
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.

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Solution

$\Rightarrow$ $({t}_{\frac{1}{2}})\propto {(\text{Initial concentration})}^{1-\text{order of Reaction}}$ $({t}_{\frac{1}{2}})\text{for}{1}^{\mathrm{st}}$ order = Independent of Concentration

$({t}_{\frac{1}{2}})\text{for}{2}^{\mathrm{nd}}$ order $\propto \frac{1}{{[A]}_{0}}$

$\Rightarrow$ Rate of first order reaction $\propto {({A}_{0})}^{1}$

Rate of second order reaction $\propto {({A}_{0})}^{2}$ rate of first order reaction and second order reaction depends on initial concentration.

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Options

A first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed.

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 ${[A]}_{0}$ .

The rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations.

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.

Solution

$\Rightarrow$ $({t}_{\frac{1}{2}})\propto {(\text{Initial concentration})}^{1-\text{order of Reaction}}$ $({t}_{\frac{1}{2}})\text{for}{1}^{\mathrm{st}}$ order = Independent of Concentration

$({t}_{\frac{1}{2}})\text{for}{2}^{\mathrm{nd}}$ order $\propto \frac{1}{{[A]}_{0}}$

$\Rightarrow$ Rate of first order reaction $\propto {({A}_{0})}^{1}$

Rate of second order reaction $\propto {({A}_{0})}^{2}$ rate of first order reaction and second order reaction depends on initial concentration.

NEET UG 2018 — Chemistry Physical Chemistry

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NEET UG 2018 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

NEET UG Physical Chemistry in other years

More NEET UG Physical Chemistry questions

Other Chemistry topics for NEET UG

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry