Question

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.

Answer 1

(A) when 2g of benzoic acid is dissolved in 25g if benzene , molecules of benzoic acid dimerise in benzene , due to this the number of particles are reduced. That’s why experimentally , we get molar mass is always greater than true value.

(b) actually , The intermolecular interactions between ethanol and acetone are very weaker and the escaping tendency of ethanol and acetone molecules increases on increase vapour pressure increases. That’s why we get, positive deviation from Raoult’ Law when we mixed ethanol and acetone.

(c) The preservation of fruits by adding concentrated sugar solution protects against bactrial action due to osmosis , due to this a bacterium  on fruit loses water, shrivels and dies.