(a) What are non-ideal solution?
(b) What role does the molecular interaction play in deciding the vapour pressure of solutions (i) alcohol and kerosene (ii) Chloroform and acetone.
When a solution does not obey Raoult’s law over the entire range of concentration, then it is called non-ideal solution.
(a) Non-ideal solutions are these solutions which
(i) do not follow Raoult’s law.
(ii) ΔHmix ≠ 0.
(iii) ΔVmix ≠ 0.
(iv) The force of attraction between A-A and B-B is not equal to A-B.
(b) In alcohol and acetone, force of attraction is less than alcohol and alcohol molecules as well as acetone and acetone molecule, therefore, vapour pressure increases.
In chlorofom and acetone, force of attraction increases due to intermolecular H-bonding, therefore, vapour pressure decreases.
Molality (m) is defined as the number of moles of the solute per kilogram (kg) of the solvent and is expressed as:
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