Question

A solute ‘S’ undergoes a reversible trimerization when dissolved in a certain solvent. The boiling point elevation of its 0.1 molal solution was found to be identical to the boiling point elevation in case of a 0.08 molal solution of a solute which neither undergoes association nor dissociation. To what percent had the solute ‘S’ undergone trimerization?

• A. (A) 30%
• B. (B) 40%
• C. (C) 50%
• D. (D) 60%

Answer 1

Answer: (A)

(A) 30%

Answer 2

Explanation:
For solute S3S⇌S310(Initially)1−aα3(at equilibrium)so vant hoff factor for solute s, i1=1−α+α3=1−2α3for other solutei2=1(as neither assosiacte nor dissociate)Now elevation of boiling point in both solution is same so molality of first solvent x vant hoff factor for first solvent = molality of second solvent x vant hoff factor for second solvent⇒0.1i1=0.08i2⇒0.1(1−2α3)=0.08⇒α=0.3⇒30% trimerization