Colligative Properties Formulae

Expression for the Concentration of Solution

Normality: The normality of the solution is defined as the number of gram equivalent of solute dissolved in 1 litre of the solution.

Molarity: The molarity of the solution is defined as the number of moles of solute per litre of the solution.

Formality: The formality of the solution is defined as the number of formula weight of the solute dissolved in 1 litre of the solution. It is used to express the concentration of ionic substances.

Molality: It is defined as the number of moles of solute dissolved in 1 Kg of the solvent.

Mole Fraction: The ration of the number of moles of the component to the total number of the moles of all components (solute and solvent) present in the solution.

Let us consider a solution containing n moles of solute and N moles of solvent

Gram per litre:  It is defined as the amount of solute in gram present in 1 litre of the solution.

Percentage by Weight (% as w/w): It is defined as the weight of the solute in gram present in 100 gm of the solution.

Percentage by Volume (% as w/v): It is defined as the weight of solute in gram present per 100 ml of the solution.

Formulas of Lowering of Vapour Pressure

P = Vapour Pressure of Pure Liquid

P_s = Vapour Pressure of the solution

M = Molecular Weight of solvent

m = Molecular Weight of solute

w = weight of solute

W = weight of solvent

Formulas of Elevation of Boiling Point

T = Boiling Point of Solution

T_o = Boiling Point of Solvent

K_b = Molal Elevation constant

Cm = Molality of the solute

H_v = Latent heat of vaporization

Formulas of Depression of Freezing Point

T = freezing point of the solution

T_o = Freezing point of the solvent

K_f = molal depression constant

H_f = Latent Heat of fusion

Formulas for Osmotic Pressure

Formulas for Van’t Hoff Factor