Question

In a first-order reaction, the concentration of the reactants is reduced to 25% in one hour. The half-life period of the reaction is:

• A. 2 hr
• B. 4 hr
• C. 1/2 hr
• D. 1/4 hr

Answer 1

The correct option is C 1/2 hr

$\frac{t_{1/2}}{t_{25\$\left(left\right)}}=\frac{0.3}{log\left(\frac{100}{25}\right)}$
$t_{1/2}=t_{25\%}\times \frac{0.3}{log4}$
$=1hr\times \frac{0.3}{0.6}=\frac{1}{2}hr$