Question

(a) 1.22g C₆H₅COOH is added into two solvents and data of ΔT_b and Kb are given as:

(i) in 100g CH₃COCH₃ ΔT_b = 0.17,

K_b = 1.7kgK/mol

(ii) In 100g benzene, ΔT_b = 0.13 and 

K_b = 2.6kg K/mol

Find out the molecular weight of C₆H₅COOH in both the cases and interpret the result.

(b) 0.1M of HA is titrated with 0.1M NaOH, calculate the pH at point. Given, K_a(HA) = 5.6 x 10^-6 and α <<1.

Answer 1

(a) (i) In first case

The conclusion is that benzoic acid dimerises in benzene as

Thus at end point the solution contains only Na A (being salt of weak acid and strong base) whose concentration is 0.05M.