Question

The saturated vapour pressure on a planet is 760 mm of Hg. The vapour density is given as $\frac{s+50}{100}kg/m^2$. Find $s$

Answer 1

This vapour pressure can be obtained only at 100${}^o$C or 373 K, that is, at boiling point of water.
Using $PV=nRTn=\frac{m}{M}$ and $\rho =\frac{m}{V}$
$\frac{PM}{\rho }=RT$
$\therefore \rho =\frac{PM}{RT}=\frac{{10}^5\times 18\times {10}^{-3}}{8.31\times 373}=0.58kg/m^3$