Types of Solutions
Solutions can be solid, liquid or gaseous. Depending upon the physical state of the solute and the solvent, there are nine possible types of solutions consisting of two components (binary solutions).
| Solute | Solvent | Example |
| Gas | Gas | Air |
| Gas | Liquid | Soda water |
| Gas | Solid | Hydrogen in palladium |
| Liquid | Gas | Humidity in air |
| Liquid | Liquid | Alcohol in water |
| Liquid | Solid | Mercury in gold |
| Solid | Gas | Camphor in air |
| Solid | Liquid | Sugar in water |
| Solid | Solid | Alloys like brass, bronze |
Liquids in Liquids
In the solution of liquids in liquids such as alcohol in water, the constituent present in smaller amounts is designated as solute and the constituent present in larger amounts is called the solvent.
When two liquids are mixed, three different situations may arise:
- Both the liquids are completely miscible, i.e., when, two liquids are mixed, they dissolve in each other in all proportions, e.g., alcohol and water, benzene and toluene.
- The liquids are partially miscible, i.e., they dissolve in each other only to a certain extent, e.g., water and phenol.
- The liquids are immiscible, i.e., they do not dissolve in each other, e.g., water and benzene, water and toluene.
The solubility of liquids in liquids generally increases with rise in temperature.
Gases in Liquids
Gases are generally soluble in liquids. Oxygen is sufficiently soluble in water, which allows the survival of aquatic life in ponds, rivers and oceans. Gases like CO2 and NH3 are highly soluble in water. The solubility of a gas in a liquid depends on the pressure, temperature and the nature of the gas and the solvent.
Effect of Pressure: The variation of solubility of a gas in a liquid with pressure is governed by Henry’s Law. Henry’s law states that the mass or mole fraction, of a gas dissolved in a solvent is directly proportional to the partial pressure of the gas.
x = Kp
Effect of temperature: The solubility of a gas in a liquid at constant pressure decreases with rise in temperature. For example, the solubility of CO2 in water at 20°C is 0.88 cm3 per cm3 of water, where as it is 0.53 cm3 per cm3 of water at 40°C. This happens because on heating a solution, containing a dissolved gas, some gas is usually expelled from the solution.
Effect of the nature of the gas and the solvent: Gases like CO2, HCl and, NH3 are highly soluble in water where as H2, O2 and N2, are sparingly soluble.
Solids in Liquids
When a solid is dissolved in a liquid, the solid is referred as the solute and the liquid as the solvent. For example, in a solution of sodium chloride in water, the solute is sodium chloride and water is the solvent. Different substances dissolve to different extent in the same solvent.