Question

The rate constant for a first order reaction is $k=7\times {10}^{-4}{s}^{-1}$. The time taken for the reactant to be reduced to $\frac{1}{4}$ of the initial concentration is

• A. 990 s
• B. 1980 s
• C. 445 s
• D. 2970 s

Answer 1

The correct option is B 1980 s

$t=\frac{2.303}{k}log\frac{1}{\frac{1}{4}}=\frac{2.303}{7\times {10}^{-4}}log4t=\frac{2.303}{7\times {10}^{-4}}\times 0.0602=1980s$