Nitrogen and hydrogen react together to form ammonia.

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{NH}}_3\left(\mathrm{g}\right)$.

$0.1 \mathrm{mol}$ of nitrogen and $0.1 \mathrm{mol}$ of hydrogen were mixed in a closed container of volume $1 {\mathrm{dm}}^3$. At equilibrium $\mathrm{n} \mathrm{mol}$ ammonia is formed. What is the concentration of hydrogen at equilibrium?

Explain why increasing the concentration of oxygen in this reaction does not affect the value of ${\mathrm{K}}_{\mathrm{c}}$.

${\mathrm{O}}_2+\mathrm{NO}\to {\mathrm{NO}}_2$.

The reaction below was carried out at a pressure of $10.00\times {10}^4 \mathrm{Pa}$ and at constant temperature.

${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right)$.

The partial pressures of nitrogen and oxygen are both $4.85\times {10}^4 \mathrm{Pa}$. Calculate the partial pressure of the nitrogen$\left(\mathrm{II}\right)$ oxide, $\mathrm{NO}\left(\mathrm{g}\right)$, at equilibrium.

When metallic mercury is shaken with a solution of mercury$\left(\mathrm{II}\right)$ nitrate a solution of mercury$\left(\mathrm{I}\right)$ nitrate is formed.

$\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{Hg}}^{2+}\left(\mathrm{aq}\right)\rightleftharpoons {{\mathrm{Hg}}_2}^{2+}\left(\mathrm{aq}\right)$.

What is the correct equilibrium expression for this reaction?