Question

It is well known that if an ordinary water is salted, its boiling point rises. Determine the change in the density of saturated water vapour at the boiling point.

Answer 1

Considering that the gas density is $\rho =M/V$, we can write the equation of state for water vapour in the form $p=\left(\rho /\mu \right)RT$, where $\rho$ and $\mu$, are the density and molar mass of water vapour. Boiling takes place when the saturated vapour pressure becomes equal to the atmospheric pressure. If the boiling point of the salted water has been raised at constant atmospheric pressure, it means that the density of saturated water vapour must have decreased.