Which among the following represents the expression for $\left(\frac{3}{4}\right)^{\text {th }}$ life of…

Which among the following represents the expression for $\left(\frac{3}{4}\right)^{\text {th }}$ life of $1^{\text {st }}$ order reaction?
  1. $\frac{k}{2.303} \log \left(\frac{4}{3}\right)$
  2. $\frac{2.303}{k} \log \left(\frac{3}{4}\right)$
  3. $\frac{2.303}{k} \log (4)$
  4. $\frac{2.303}{k} \log (3)$

Solution

For first order reaction, $t=\frac{2.303}{k} \log \frac{a}{a-x}$ if $t=t_{3 / 4}$ and $x=\frac{3}{4} a$ Then, $t_{3 / 4}=\frac{2.303}{k} \log \frac{a}{a-\frac{3 a}{4}}$ $\Rightarrow \quad t_{3 / 4}=\frac{2.303}{k} \log 4$

Asked in: AP EAMCET 2021 (23 Aug Shift 2)

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