For first order reaction the concentration of reactant decreases form $0 \cdot 2$ to $0.1 \mathrm{M}$ in 100…

For first order reaction the concentration of reactant decreases form $0 \cdot 2$ to $0.1 \mathrm{M}$ in 100 minutes. What is the rate constant of the reaction?
  1. $6.93 \mathrm{~min}^{-1}$
  2. $69 \cdot 3 \mathrm{~min}^{-1}$
  3. $6.93 \times 10^{-3} \mathrm{~min}^{-1}$
  4. $144 \cdot 3 \mathrm{~min}^{-1}$

Solution

$\begin{aligned} \mathrm{k} &=\frac{0.693}{\mathrm{t}_{1 / 2}} \text { (For first order reaction) } \\ \therefore \mathrm{k} &=\frac{0.693}{100 \mathrm{~min}}=6.93 \times 10^{-3} \mathrm{~min}^{-1} \end{aligned}$

Asked in: MHT CET 2020 (19 Oct Shift 2)

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