Question

The rate constant for a first order reaction is $4.606\times {10}^{-3}{s}^{-1}$. The time required to reduce $2.0g$ of the reactant to $0.2g$ is:

• A. $200s$
• B. $500s$
• C. $100s$
• D. $100s$

Answer 1

The correct option is B $500s$

For a first order reaction,
$k=\frac{2.303}{t}log\frac{[R{]}_0}{\left[R\right]}$
$\Rightarrow t=\frac{2.303}{4.606\times {10}^{-3}{s}^{-1}}log\frac{2}{0.2}=\frac{2.303\times {10}^3}{4.606}=500s$