CBSE Class 12 · 2006 · Foreign · SolutionsShort Answer

(a) Non-ideal solutions are those which do not obey Raoult's law over the entire range of concentration; for them ${\Delta }_{mix}H\ne 0$ and ${\Delta }_{mix}V\ne 0$.
(b)(i) Alcohol + acetone: acetone molecules break the hydrogen bonds between alcohol molecules; the A–B attractions are weaker, molecules escape more readily, and the vapour pressure is higher than ideal (positive deviation).
(ii) Chloroform + acetone: a new hydrogen bond forms between the H of CHCl${}_3$ and the carbonyl O of acetone; the A–B attractions are stronger, escape is hindered, and the vapour pressure is lower than ideal (negative deviation).