The colligative properties of solution depend on the total number of solution.
since the eletrolytes ionise and give more than one particle per formula unit in solution the colligative effect of an eletrolyte solution is alaways greater than that of a non electrolyte of the same molar concentration.
The molar mass of acetic acid in a solution of benzene solvent is greater than its formula molar mass because two CH3COOH molecules form a dimer (CH3COOH)2 in solution. But we know that the molar mass is defined as the mass of 6.023 x 1023 particles of the substance. In case of a normal solute like CH3COOH, the molar mass of acetic acid is equal to the mass of 6.023 x 1023 molecules of formula CH3COOH. While in solution the solution dimerises and becomes a bigger molecule like (CH3COOH)2. Now in this case the molar mass of the solute is equal to the mass of 6.023 x 1023 units of formula (CH3COOH)2. Naturally, this molar mass is larger than the normal formula molar mass. In case of association, Van’t Hoff factor is less than 1, therefore,
MB (abnormal) > MB (normal) when i < 1.
Calculate (a) molality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL-1.
Molarity (M) is defined as number of moles of solute dissolved in one litre (or one cubic decimetre) of solution.
(a) Mol. mass of
Volume of solution = 4.3 L
(b) Number of moles present in 1000 ml of 0.5M H2SO4= 0.5 mol
therefore number of moles present in 30ml of 0.5M H2SO4=mol =0.015mol
therefore molarity =0.015/0.5L
thus molarity is 0.03M
Molality (m) is defined as the number of moles of the solute per kilogram (kg) of the solvent and is expressed as: