According to Raoult's law the partial vapour pressure of each volatile compound in any solution is directly proportional to its mole fraction
if the vapour pressure is higher then solution is said to exhibit positive deviation
Positive deviation is shown by ethanol and water, cyclohexane and ethanol, acetone and diethylether etc.
(i) A—B interaction is weaker than A—A or B—B in positive deviation.
If the vapour pressure is lower then solution then solution is said to exhibit negtive deviation.
Negative deviation is shown by chloroform and acetone, methanol and acetic acid, H2O and HCl, H2O and HNO3 etc.
(ii) A—B interaction is stronger than A—A or B—B in negative deviation.
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,
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: