Question

Molecules of benzoic acid (C₆H₅COOH) dimerise in benzene. ‘w’ g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2 K. If the percentage association of the acid to form dimer in the solution is 80, then w is :
(Given that Kf = 5 K kg mol⁻¹, Molar mass of benzoic acid = 122 g mol⁻¹)
(A) 2.4 g (B) 1.0 g
(C) 1.5 g (D) 1.8 g

Answer 1

Answer:

The molecular weight of benzoic acid in benzene as determined by depression in freezing point method corresponds to

Molecules of benzoic acid. dimerise in benzene. 'w' g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2 K.