Question

What happens to equilibrium when the volume is increased?

Answer 1

Effect of volume on equilibrium:

1. Pressure change will not affect the equilibrium concentration of solids and liquids. It will only affect the gaseous reactions.
2. For example - $$\begin{gathered} \mathrm{CO}\left(\mathrm{g}\right)+3{\mathrm{H}}_2\rightleftharpoons {\mathrm{CH}}_4\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ 4\mathrm{moles}2\mathrm{moles} \end{gathered}$$
3. There are four moles of reactants that react to form two moles of product.
4. If the volume is halved, then the total pressure will be doubled as pressure is inversely proportional to volume.
5. We know that pressure is directly proportional to the number of moles.
6. As the pressure is increased, the equilibrium will shift in a direction to neutralize the effect i.e, in the direction of the decrease in the pressure i.e., in the direction of the decrease in the number of moles.
7. So, the reaction will shift in the forward direction.
8. If the pressure is decreased, the equilibrium will shift in a direction to neutralize the effect i.e, in the direction of an increase in the number of moles.
9. So, the reaction will shift in the reverse direction.