For a first-order reaction,the concentration of the reactant decreases from $0.8 \, M$ to $0.4 \, M$ in $15 \, \text{minutes}$. The time required for the concentration to change from $0.1 \, M$ to $0.025 \, M$ is ....... $\text{min}$.

Time required for completion of $99.9 \%$ of a First order reaction is . . . . . . times of half life $(t_{1/2})$ of the reaction.

The half-life of a first order reaction $X \to Y$ is $100 \ min$. The concentration of $X$ would be reduced to $10 \%$ of the initial concentration in .......... $min$.

$A$ first order reaction is $50 \%$ completed in $16 \ minutes$. Find the percentage of reactant reacting in $32 \ minutes$. (in $\%$)

Dissociation of $N_2O_5$ dissolved in $CCl_4$ at constant temperature: $N_2O_{5(soln)} \to 2NO_{2(soln)} + \frac{1}{2}O_{2(g)}$. This is a first order reaction. The velocity constant is $5.0 \times 10^{-4} \ s^{-1}$. The initial concentration of $N_2O_5$ is $0.25 \ mol \ L^{-1}$. How much time is required to produce $0.20 \ mol \ L^{-1}$ concentration of $NO_2$ (in $s$)?

At $298 \ K$,for a first order reaction $(A \rightarrow P)$ the following graph is obtained. The rate constant (in $s^{-1}$) and initial concentration (in $mol \ L^{-1}$) of '$A$' are respectively ($y$-axis $= \ln(a-x)$; $x$-axis $=$ time in sec).