The time required for completion of 93 . 75 % of a first order reaction is x minutes. The half life of it…

The time required for completion of 93.75% of a first order reaction is x minutes. The half life of it (in minutes) is
  1. x8
  2. x2
  3. x4
  4. x3

Solution

\(\begin{aligned} & t_{1 / 2}=\frac{0.0693}{k_1} \\ & \text {Also, } t_{93.75}=\frac{2.303}{k_1} \log \cdot \frac{100}{100-93.75} \\ & =\frac{2.303}{k_1} \log \cdot \frac{100}{6.25} \\ & =\frac{2.303}{k_1} \log 2^4 \\ & \frac{4 \times 2.303 \times \log 2}{k_1}=\frac{4 \times 0.693}{k_1}=4 t_{1 / 2}\end{aligned}\) \(\begin{aligned} & 4 t_{1 / 2}=\mathrm{x} \\ & t_{1 / 2}=\mathrm{x} / 4 \end{aligned}\) So correct option is (3) *

Asked in: JEE-TOPICTESTS-CHEMISTRY

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