Question:
Calculate the half-life of a first order reaction from their rate constants given below:
(i) 200 s−1 (ii) 2 min−1 (iii) 4 years−1
Solution:
(i) Half life, $t_{1 / 2}=\frac{0.693}{k}$
$=\frac{0.693}{200 \mathrm{~s}^{-1}}$
$=3.47 \times 10^{-3} \mathrm{~s}$ (approximately)
(ii) Half life, $t_{1 / 2}=\frac{0.693}{k}$
$=\frac{0.693}{2 \mathrm{~min}^{-1}}$
= 0.35 min (approximately)
(iii) Half life, $t_{1 / 2}=\frac{0.693}{k}$
$=\frac{0.693}{4 \text { years }^{-1}}$
= 0.173 years (approximately)
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