Chemistry - Liquid Solution Question with Solution | TestHub

As we know
$\frac{{\mathrm{p}}^{\mathrm{o}}-\mathrm{p}}{{\mathrm{p}}^{\mathrm{o}}}={\mathrm{x}}_1=$mole fraction of solute
The ratio$\frac{\left({\mathrm{p}}^{\mathrm{o}}-\mathrm{p}\right)}{{\mathrm{p}}^{\mathrm{o}}}$is the relative lowering of vapour pressure, which is equal to 0.0125 here.
So${\mathrm{X}}_1=0.0125$
The relation between the mole fraction and molality is
$\left(\frac{1}{{\mathrm{X}}_1}-1\right)=\frac{1000}{\mathrm{m}\times 18}$(molecular weight of${\mathrm{H}}_2\mathrm{O}=18$)
or$\left(\frac{1}{0.0125}-1\right)=\frac{100}{\mathrm{m}\times 18}$w
$\mathrm{m}=\mathrm{0.70\; m}$