Question

(a) Mr. Raju has determined the molecular masses of different solutes in different solvents by osmotic pressure measurements and presented them in the following table. Please help him to complete the table.

Solute	Solvent	Theoretical Molecular Mass	Experimental Molecular Mass
NaCl	Water	A	A/2
Benzoic	Benzene	B	—
Acid	Water	C	—
Urea	Benzene	D	—
Acetic acid	Water	E	—
CaCl2	Water	F	—
Glucose	Water	G	—
Ai2(So4)3			—

(b) The extent of deviation from ideal behaviour of a solution is explained by van’t Hoff factor, i. What is meant by van’t Hoff factor?

Answer 1

(a) 2B, C, 2D, E/3, F, G/5.

(b) 2B and 2 D are due to association

i = \(\frac{Normal \,molar \,mass}{Abnormal \,molar \,mass}\)

OR

i = \(\frac{Observed\,Colligative\, Property}{Calculated\,Colligative\, property}\)