State and explain Kohlrausch law of independent migration of ions. How is it useful to determine the molar conductivity of weak electrolytes at zero concentration?

Write the Nernst equation and calculate emf of the following cell at $298 \mathrm{K}:$
 $\mathrm{M}\mathrm{g}\left(\mathrm{s}\right) \left| \mathrm{M}{\mathrm{g}}^{2+}\left(0.001\mathrm{M}\right) \right|\left| \mathrm{C}{\mathrm{u}}^{2+}\left(0.0001\mathrm{M}\right) \right| \mathrm{C}\mathrm{u}\left(\mathrm{s}\right)$

(Given ${\mathrm{E}}_{{\mathrm{Mg}}^{+2}/\mathrm{Mg}}^{\circ }=-2.36, {\mathrm{E}}_{{\mathrm{Cu}}^{+2}/\mathrm{Cu}}^{\circ }=0.34$)

Iodine $\left({\mathrm{I}}_2\right)$ and bromine $\left({\mathrm{Br}}_2\right)$ are added to a solution containing iodide $\left({\mathrm{I}}^{-}\right)$ and bromide $\left({\mathrm{Br}}^{-}\right)$ ions. What is the reaction occurred if the concentration of each species is $1 \mathrm{M}$?

The electrode potentials for the reactions are ${{\mathrm{E}}^{°}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}=0.54 \mathrm{V}$ and ${\mathrm{E}}_{{\mathrm{Br}}_2/{\mathrm{Br}}^{-}}^{°}=1.08 \mathrm{V}$, respectively.

$\mathrm{MgO}$, $\mathrm{CuO}$ and ${\mathrm{Na}}_2\mathrm{O}$

Which of these oxides are reduced by hydrogen?