Question

Arrange the following according to increasing vapor pressure:

1m NaCl, 1m CaCl₂, 1m C₆H₁₂O₆, 1m AlCl₃

Answer 1

This property depend on the number of particles in solution.

More the number of particles, lower the vapour pressure.

All are 1M solutions, so the numbers depend on ionization in solution:

NaCl → Na+ Cl- (2 particles)

CaCl₂ → Ca+ Cl- Cl- (3 particles)

C₆H₁₂O₆ (no ionization, so 1 particle)

AlCl₃ → Al+ Cl- Cl- Cl- (4 particles)

Therefore, arrangement according to

Increasing vapour pressure AlCl₃ < CaCl₂ < NaCl < C₆H₁₂O₆