$2{\mathrm{NOCl}}_{\left(\mathrm{g}\right)}\rightleftharpoons 2{\mathrm{NO}}_{\left(\mathrm{g}\right)}+{{\mathrm{Cl}}_2}_{\left(\mathrm{g}\right)}$

In an experiment, $2.0$ moles of $\mathrm{NOCl}$ was placed in a one-litre flask and the concentration of $\mathrm{NO}$ after equilibrium established, was found to be $0.4 \mathrm{mol}/\mathrm{L}$. The equilibrium constant ${\mathrm{K}}_{\mathrm{c}}$ at $30 °\mathrm{C}$ is a$\times {10}^{-4}$. Calculate the value of $\mathrm{a}$ and give answer to the nearest integer value

${\mathrm{Ka}}_1,{\mathrm{Ka}}_2$ and ${\mathrm{Ka}}_3$ are the respective ionization constants for the following reactions $\left(\mathrm{a}\right),\left(\mathrm{b}\right)$ and $\left(\mathrm{c}\right)$.

(a) ${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{HC}}_2{\mathrm{O}}_4^{-}$

(b) ${\mathrm{HC}}_2{\mathrm{O}}_4^{-}\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{HC}}_2{\mathrm{O}}_4^{2-}$

(c) ${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4\rightleftharpoons 2{\mathrm{H}}^{+}+{\mathrm{C}}_2{\mathrm{O}}_4^{2-}$

The relationship between ${\mathrm{K}}_{{\mathrm{a}}_1},{ \mathrm{K}}_{{\mathrm{a}}_2}$ and ${\mathrm{K}}_{{\mathrm{a}}_3}$ is given as

At $298 \mathrm{K}$, the equilibrium constant is $2\times {10}^{15}$ for the reaction:

$\mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)$

The equilibrium constant for the reaction

$\frac{1}{2}{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+\mathrm{Ag}\left(\mathrm{s}\right)\rightleftharpoons \frac{1}{2}\mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)$ is $\mathrm{a}\times {10}^{-8}$. The value of $\mathrm{a}$ is..............(Nearest integer value)