Question

$4.6c{m}^3$ of methyl alcohol is dissolved in $25.2$g of water. Calculate mole fraction of methyl alcohol and water. (Given density of methyl alcohol = $0.7952gc{m}^{-3}$ and $C=12,H=1,O=16$)

Answer 1

Density= $\frac{mass}{Volume}=\frac{m}{4.6}$

$m=0.7952\times 4.6=3.657g$

$n_A=\frac{25.2}{18}=1.4$

Molar mass of $C{H}_{3}OH=32g$

$n_B=$ Number of moles of solute= $\frac{3.657}{32}=0.114$

Total number of moles= $0.114+\frac{25.12}{18}$

$\Rightarrow n_A+n_B=1.514$

Mole fraction of $C{H}_{3}OH$

$\Rightarrow x_B=\frac{n_B}{n_A+n_B}=\frac{0.114}{1.514}=0.075$