- A solution is a homogeneous mixture of two or 9.
more chemically non-reacting substances. - The components of a solution generally cannot be separated by filtration, settling or centrifuging.
A solution may be classified as solid, liquid or a gaseous solution.
Solubility is defined as the amount of solute in a saturated solution per 100g of a solvent. - The solubility of a gas in a liquid depends upon
(a) the nature of the gas and the nature of the liquid,
(b) the temperature of the system, and
(c) the pressure of the gas. - The effect of pressure on the solubility of a gas in a liquid is governed by Henry’s Law. It states that the solubility of a gas in a liquid at a given temperature in directly proportional to the partial pressure of the gas Mathematically, P = KHX where P is the partial pressure of the gas; and X is the mole fraction of the gas in the solution and KH is Henry’s Law constant.
- The vapour pressure of a liquid is the pressure exerted by its vapour when it is in dynamic equilibrium with its liquid, in a closed container
- According to Raoults Law, the vapour pressure of a solution containing a non-volatile solute is directly proportional to the mole fraction of the solvent ( XA). The proportionality constant being the vapour pressure of the pure solvent, i.e., P× XA or P = P° XA.
- A solution which obeys Raoult’s Law at all concentrations and temperatures is known as an ideal solution.
- Characteristics of an ideal solution:
- (a) ∆sol V = 0, i.e., there is no change in volume when an ideal solution is formed.
- (b) ∆sol H= 0; i.e., heat is neither evolved nor absorbed during the formation of an ideal solution.
- (a) The solution shows positive deviation from Raoult’s Law if its vapour pressure is higher than that predicted by Raoult’s Law.
- (b) The solution shows negative deviation if its vapour pressure is lower than that predicted by Raoult’s Law.
- Colligative properties of solutions are those properties which depend only upon the number of solute particles in the solution and not on their nature. Such properties are
- (a) Relative lowering in vapour pressure,
- (b) Elevation of boiling point,
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