We observe abnormal molecular masses when the solute is an electrolyte and undergo either into association or dissociation.
One unit of an electrolyte compound separates into two or more particles when it dissolves and colligative properties depends on the number of solute particles.
Each NaCl unit dissociates into two ions-Na+ and CI–. Thus, the colligative properties of a 0.1 m solution of NaCl should be twice as great as those of a 0.1 m solution containing a non-electrolyte, such as glucose or sucrose.
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.
Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.
Let the total mass of the solution be 100g and mass of benzene be 30 g
therefore mass of tetrachloride= (100-30)g = 70g
Molar mass of benzene,
Molality (m) is defined as the number of moles of the solute per kilogram (kg) of the solvent and is expressed as:
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