Question

Explain why molecular mass of ethanoic acid when determined by colligative properties of its solutions is abnormal. Suggest the value of van’t Hoff factor in this case.

Answer 1

Ethanoic acid undergoes dimerisation in solution. If two moles of ethanoic acid associate to give exactly one mole of the dimer,

\[\ce{\underset{2 moles}{2CH3COOH} <=> \underset{1 mole}{(CH3COOH)2}}\]

`i = "No. of particles in solution"/"No. of particles added"`

= `1/2`

= 0.5