Question

Show that for a dilute solution `Delta p = (wM)/(WM') xx p^circ`

where, w = mass of solute, W = mass of solvent, M' = molecular mass of solute. M = molecular mass of solvent and p° = vapour pressure of pure solvent.

Answer 1

According to Raoult’s law, for a dilute solution,

`(p^circ - p)/p^circ = (w M)/(W M')`

or `(Delta p)/p^circ = (w M)/(W M')`

or `Delta p = p^circ M xx w/(W M')`