Question

What is Van't Hoff factor ? Under what conditions Van't Hoff factor is 

(a) >1 

(b) = 1

(c) < 1. Explain.

Answer 1

Van't Hoff factor (i) is the ratio of natural molecular mass (M_n) to the observed molecular mass (M₀)

(a) Now, i > 1 when M_n > M₀. This can happen in case of electrolytes when the solute undergoes dissociation in solution and thus corresponds to lower value of molecular mass that is observed from measurement of colligative property.

(b) i = 1 when M_n = M₀ .This can occur if the solute does not undergo dissociation or association in solution.

(c) i < 1 when M_n < M₀ . This can happen if the solute undergoes association in solution so that the value of observed molecular mass becomes larger.