Question

Explain why the mol.mass of nacl is determined by the elevation of boiling point method is half its actual molecularmass

Answer 1

Since NaCl dissociates in water as Na+ and Cl-, we get two ions in the solution. Now elevation in boiling point being a collagative property it depends only on the number of solute particles. So actual number of particles in solution now is 2. Such systems are known to exhibit abnormal molar mass.

According to Vant Hoff,

i = Observed collagative property/Actual collagative property