In a first order reaction if concentartion of reactant drops from $0.8 \mathrm{~mol} \mathrm{~L}^{-1}$ to $0.4 \mathrm{~mol} \mathrm{~L}^{-1}$ in 15 minute. What is the time required to drop concentration from $0.1 \mathrm{~mol} \mathrm{~L}^{-1}$ to 0.025 mol $\mathrm{L}^{-1}$.

Calculate the time required for reactant to decrease the concentration from $100 \%$ to $20 \%$, if rate constant of first order reaction is 0.02303 hours $^{-1}$.

What is the rate of formation of $\mathrm{O}_2$ for the reaction stated below?

$$\begin{aligned} & 2 \mathrm{~N}_2 \mathrm{O}_{5(8)} \longrightarrow 4 \mathrm{NO}_{2(g)}+\mathrm{O}_{2(\mathrm{~g})} \\ & {\left[\frac{\mathrm{d}\left[\mathrm{~N}_2 \mathrm{O}_5\right]}{\mathrm{dt}}=0.02 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}\right]} \end{aligned}$$

Rate law for the reaction $2 \mathrm{NO}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{NOCl}$ is rate $=\mathrm{k}[\mathrm{NO}]^2\left[\mathrm{Cl}_2\right]$. When will the value of k increase?