Find the rate of disappearance of $B$ for the reaction $2 \mathrm{~A}+\mathrm{B} \longrightarrow 2 \mathrm{C}+\mathrm{D}$, from following.

For the reaction

$$ \mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{NH}_{3(\mathrm{~g})} $$

$\mathrm{N}_{2(\mathrm{~g})}$ disappears at the rate of $2 \times 10^{-4} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}$. Find the rate of $\mathrm{NH}_3$ formation.

Half life of a first order reaction is 3 hours. Calculate the value of $\frac{[\mathrm{A}]_0}{[\mathrm{~A}]_{\mathrm{t}}}$ after 8 hours.

$60 \%$ of a first order reaction is completed in 60 minute. What is the time taken by reactant to decompose half of its original amount?