What is the value of rate constant of first order reaction, if it takes 15 minutes for consumption of $20…
What is the value of rate constant of first order reaction, if it takes 15 minutes for consumption of $20 \%$ of reactants?
- $1 \cdot 84 \times 10^{-2} \min ^{-1}$
- $1 \cdot 38 \times 10^{-2} \min ^{-1}$
- $1 \cdot 07 \times 10^{-2} \min ^{-1}$
- $1 \cdot 48 \times 10^{-2} \min ^{-1}$
Solution
$[\mathrm{A}]_{0}=$ Original amount of reactant $=100$
$[\mathrm{A}]_{t}=$ Reactant remaining unreacted $=100-20=80$
For first order reaction,
$\begin{aligned}
\mathrm{k} &=\frac{2.303}{\mathrm{t}} \log _{10} \frac{[\mathrm{A}]_{0}}{[\mathrm{~A}]_{t}} \\
\therefore \mathrm{k} &=\frac{2.303}{15 \mathrm{~min}} \log _{10} \frac{100}{80}=0.0148 \mathrm{~min}^{-1} \\
\therefore \mathrm{k} &=1.48 \times 10^{-2} \mathrm{~min}^{-1}
\end{aligned}$
Asked in: MHT CET 2020 (16 Oct Shift 2)
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