114.

(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.

Answer:

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) ΔH_mix ≠ 0.
(iii) ΔV_mix ≠ 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.