Chemical Kinetics - Result Question 2
####2. If the rate constant for a first order reaction is $k$, the time $(t)$ required for the completion of $99 %$ of the reaction is given by:
[2019]
(a) $t=0.693 / k$
(b) $t=6.909 / k$
(c) $t=4.606 / k$
(d) $t=2.303 / k$
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Solution:
- (c) For a first order reaction,
$ t=\frac{2.303}{k} \log \frac{[A] _{o}}{[A]} $
for $99 %$ completion of the reaction,
$ \begin{aligned} & t=\frac{2.303}{k} \log \frac{100}{100-99} \\ & t=\frac{2.303}{k} \log 10^{2} \\ & t=\frac{4.606}{k} \end{aligned} $
