The decomposition of phosphine, ${\mathrm{PH}}_3$, proceeds according to the following equation :

$4{\mathrm{PH}}_3\left(\mathrm{g}\right)⟶{\mathrm{P}}_4\left(\mathrm{g}\right)+6{\mathrm{H}}_2\left(\mathrm{g}\right)$

It is found that the reaction follows the following rate equation:

Rate$=\mathrm{k}\left[{\mathrm{PH}}_3\right]$

The half-life of ${\mathrm{PH}}_3$ is $37.9 \mathrm{s}$ at $120°\mathrm{C}$

How much time is required for $3/4\mathrm{th}$ of ${\mathrm{PH}}_3$ to decompose.

The decomposition reaction $2{\mathrm{N}}_2{\mathrm{O}}_5\left(\mathrm{g}\right)\stackrel{ ∆ }{\to }2{\mathrm{N}}_2{\mathrm{O}}_4\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$ is started in a closed cylinder under the isothermal isochoric condition at an initial pressure of $1 \mathrm{atm}$. After $\frac{\mathrm{Y}}{10}\times {10}^3\mathrm{ }\mathrm{s}$ , the pressure inside the cylinder is found to be $1.45\mathrm{ }\mathrm{a}\mathrm{t}\mathrm{m}$ . If the rate constant of the reaction is $5\times {10}^{-4}{\mathrm{s}}^{-1}$, assuming ideal gas behaviour, the value of $\mathrm{Y}$ is(nearest integer)

The given plots represent the variation of the concentration of a reactant $\mathrm{R}$ with time for two different reactions $\left(\mathrm{i}\right) \mathrm{and} \left(\mathrm{ii}\right)$. The respective orders of the reaction are
(i) 

(ii)