Question

Acetic acid associates as dimers in benzene. What is the Van’t Hoff factor (i) if the degree of association of acetic acid is 50%?

(a) 0.25

(b) 0.50

(c) 0.75

(d) 0.40

I had been asked this question at a job interview.

Query is from Abnormal Molar Masses topic in section Solutions of Chemistry – Class 12

Answer 1

Correct option is (c) 0.75

Explanation: Given,

Degree of association (α) = 50% = 0.5

Number of molecules associated (n) = 2

Let the Van’t Hoff factor = i

We know that for solutes that associate in solution, i = 1 + ((1/n) -1) x α

           = 1 + ((1/2) – 1) x 0.5

           = 1 – (0.5 x 0.5)

           = 0.75

Therefore, the Van’t Hoff factor is equal to 0.75.