Question

Find the specific rate constant, if half life of a first-order reaction is $1386seconds$:

• A. $5.0\times {10}^{-2}{s}^{-1}$
• B. $5.0\times {10}^{-3}{s}^{-1}$
• C. $0.5\times {10}^{-5}{s}^{-1}$
• D. $0.5\times {10}^{-3}{s}^{-1}$

Answer 1

The correct option is D $0.5\times {10}^{-3}{s}^{-1}$

$t_{\frac{1}{2}}=1386s$ (for first order reaction)
$\Rightarrow t_{\frac{1}{2}}=\frac{0.693}{k}$
$k=\frac{0.693}{1386}=5\times {10}^{-4}{\text{s}}^{-1}$