The half time of the first order decomposition of nitramide is $2.1$ hour at $15 °\mathrm{C}$.

${\mathrm{NH}}_2{\mathrm{NO}}_2\left(\mathrm{aq}.\right)\to {\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

If $6.2 \mathrm{g}$ of ${\mathrm{NH}}_2{\mathrm{NO}}_2$ is allowed to decompose, calculate time taken for ${\mathrm{NH}}_2{\mathrm{NO}}_2$ to decompose $99\%$.

For the elementary reaction $2 \mathrm{A}+{\mathrm{B}}_2⟶2\mathrm{AB}$. Calculate how much the rate of reaction will change if the volume of the vessel is reduced to one third of its original volume?

A first order reaction $75\%$ Completed in $72 \min$. How long time will it take for $87.5\%$ completion

A first order reaction has a rate constant $1.5\times {10}^{-3}{\sec }^{-1}$. How long will $5.0 \mathrm{g}$ of this reactant take to reduce to$1.25 \mathrm{g}$.

Report your answer in the nearest integer value.

A drug is known to be ineffective after it has decomposed $30\%$. The original concentration of a sample was $500$ units / $\mathrm{mL}$. when analyzed $20$ months later, the concentration was found to be $420$ units/$\mathrm{mL}$ . Assuming that decomposition is of I order, what will be the expiry time of the drug?