Find the rate constant of first order reaction in second having half-life 2.5 hour?

Find the rate constant of first order reaction in second having half-life 2.5 hour?
  1. $6.9 \times 10^{-5} \mathrm{sec}^{-1}$
  2. $8.4 \times 10^{-5} \mathrm{sec}^{-1}$
  3. $4.3 \times 10^{-5} \mathrm{sec}^{-1}$
  4. $7.7 \times 10^{-5} \mathrm{sec}^{-1}$

Solution

$\begin{aligned} & K=\frac{0.693}{2.5 \times 60 \times 60} \\ & =7.7 \times 10^{-5} \mathrm{sec}^{-1}\end{aligned}$

Asked in: MHT CET 2022 (10 Aug Shift 2)

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