Question

What happens to equilibrium when pressure is increased?

Answer 1

Effect of pressure on equilibrium:

1. A pressure shift caused by changing the volume might impact the yield of products in a gaseous reaction when the total number of moles of gaseous reactants and gaseous products are different.
2. The volume and concentration of a solution/liquid are virtually independent of pressure in a heterogeneous equilibrium, the influence of pressure variations on solids and liquids can be neglected.
3. For example, ${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{NH}}_3\left(\mathrm{g}\right)$, there is a total of four moles of gaseous molecules in the left direction and two gaseous molecules in the right direction of the reaction. When the pressure increases, the equilibrium position shifts to the right in order to decrease the number of gaseous molecules.
4. Another example, ${\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{I}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{HI}\left(\mathrm{g}\right)$, that there are two moles of gaseous molecules on each side. When pressure increases, the equilibrium position is unchanged.