The effect of pressure on solubility depends on whether the solute is a gas, liquid, or solid:
- Gaseous solutes in liquids
- Pressure has a major effect.
- Increasing pressure above the liquid increases the solubility of the gas.
- This happens because higher pressure pushes more gas molecules into the liquid.
- This relationship is explained by Henry’s Law, which states that the solubility of a gas in a liquid is directly proportional to the pressure of that gas above the liquid.
- Example: Carbonated drinks (soda) are bottled under high pressure, so more carbon dioxide dissolves. When the bottle is opened, pressure decreases and the gas escapes as bubbles.
- Solid or liquid solutes in liquids
- Pressure has little to almost no effect.
- The solubility of solids or liquids does not significantly change with pressure because liquids and solids are nearly incompressible.
- Thus, their solubility depends more on temperature than on pressure.
In summary:
- Pressure strongly affects the solubility of gases in liquids.
- Pressure has negligible effect on the solubility of solids and liquids in liquids.