$A$ first order reaction is $60 \%$ complete in $20 \ min$. How long will the reaction take to be $84 \%$ complete (in $min$)?

For a first order reaction $A \rightarrow \text{Products}$,initial concentration of $A$ is $0.1 \, M$,which becomes $0.001 \, M$ after $5 \, \min$. Rate constant for the reaction in $\min^{-1}$ is .... .

If the half-life $(t_{1/2})$ for a first order reaction is $1 \text{ minute}$,then the time required for $99.9\%$ completion of the reaction is closest to

The decomposition of the smog component peroxyacetyl nitrate $(PAN)$ follows a first-order reaction into peroxyacetyl radical and $NO_{2(g)}$,with a half-life of $32 \ min$.
$CH_3COONO_2 \to CH_3COO^{\bullet} + NO_2$
If the initial concentration of $PAN$ in an air sample is $5.0 \times 10^{14} \ molecules/L$,what will be the concentration after $1.5 \ hr$?

The decomposition of benzene diazonium chloride is a first order reaction. The time taken for the decomposition of $\frac{1}{4}$ and $\frac{1}{10}$ of its initial concentration are $t_{1/4}$ and $t_{1/10}$ respectively. The value of $\frac{t_{1/4}}{t_{1/10}} \times 100$ is (Given: $\log 2 = 0.3, \log 3 = 0.477$)

Which one of the following formulas represents a first-order reaction?