Question

Calculate the amount of benzoic acid to be dissolved in of benzene so that boiling point

Answer 1

Answer:

Explanation:

Tb = Kb * M

In first case,

∆Tb = Kb * m = Kb* Wt.of solute/Mol. wt. of solute

Or 0.17 = 1.7 * 1.22/M *1000 * 10-3

Or M = 122

Thus the benzoic acid exists as a monomer in acetone

(ii) ∆Tb = Kb * Wt. of solute/Mol. wt. of solute

Or 0.13 = 2.6 * 1.22/M’ * 100 * 10-3

M’ = 224

NOTE :Double the expected molecular weight of benzoic acid (244) in acetone solution indicates that benzoic acid exists as a dimer in acetone.