A sample of liquid $\mathrm{H}_2 \mathrm{O}$ of mass 18.0 g is injected into an evacuated 7.6 L flas

Question

A sample of liquid $\mathrm{H}_2 \mathrm{O}$ of mass 18.0 g is injected into an evacuated 7.6 L flask maintained at $27.0^{\circ} \mathrm{C}$. If vapour pressure of $\mathrm{H}_2 \mathrm{O}$ at $27^{\circ} \mathrm{C}$ is 24.63 mm Hg , what weight percentage of the water will be vapourised when the system comes to equilibrium? Assume water vapours behaves as an ideal gas. The volume occupied by the liquid water is negligible compared to the volume of the container:

Professor PC Thomas Classes · Answer

(a) Initial mass of $\mathrm{H}_2 \mathrm{O}(l)=18 \mathrm{~g}$; 
$ n_{\mathrm{H}_2 \mathrm{O}}(g)=\frac{\left(\frac{24.63}{760}ight) 	imes 7.6}{0.0821 	imes 300} \Rightarrow 0.01 $
$\% \mathrm{wt}$. of $\mathrm{H}_2 \mathrm{O}$ vaporised $=\frac{0.01 	imes 18}{18} 	imes 100$ 
$ \Rightarrow \quad 1 \% $