Give reasons for the following :
(a) When 2g of benzoic acid is dissolved in 25 g of benzene, the experimentally determined molar mass is always greater than the true value.
(b) Mixture of ethanol and acetone shows positive deviation from Raoult's Law.
(c) The preservation of fruits by adding concentrated sugar solution protects against bacterial action.

Explanation

(a) Molecules of benzoic acid dimerise in benzen. the number of particles are reduced.
(b) The intermolecular interactions between ethanol and acetone are weaker/the escaping tendency of ethanol and acetone molecules increases on mixing/the vapour pressure increases.
(c) Due to osmosis, a bacterium on fruit loses water, shrivels and dies