Half life of zero order reaction $\mathrm{A} \rightarrow$ product is 1 hour, when initial concentration of reaction is $2.0~\mathrm{mol~L}^{-1}$. The time required to decrease concentration of A from 0.50 to $0.25~\mathrm{mol~L}^{-1}$ is:

JEE Main · 2025 · 04 Apr 2025 · Shift 2 · Chemical Kinetics

Half life of zero order reaction

A \to

product is 1 hour, when initial concentration of reaction is

2.0 mol L^{- 1}

. The time required to decrease concentration of A from 0.50 to

0.25 mol L^{- 1}

is:

Answer: (C)

For a zero-order reaction the rate constant is independent of concentration and the half-life is

t_{1/2} = \frac{[ A ] _{0}}{2 k}

. With

t_{1/2} = 60 min

[A]_{0} = 2.0 mol L^{- 1}

, the rate constant is

k = \frac{2.0}{2 \times 60} = \frac{1}{60} mol L^{- 1} mi n^{- 1}

. Since concentration falls linearly through

[A]_{0} - [A]_{t} = k t

, the time to pass from

0.50

0.25 mol L^{- 1}

t = \frac{0.50 - 0.25}{1/60} = 15 min

. The required time is fifteen minutes.

JEE Main · 2025 · 04 Apr 2025 · Shift 2 · Single correct option