Question

Mole fraction of ethanol $\left(C_2{H}_{5}OH\right)$ in ethanol-water system is $0.25$. Thus, it has :

• A. $25\%$ ethanol by weight of solution
• B. $75\%$ water by weight of solution
• C. $46\%$ ethanol by weight of solution
• D. $54\%$ water by weight of solution

Answer 1

Answer: (C), (D)

The correct options are
C $46\%$ ethanol by weight of solution
D $54\%$ water by weight of solution

$Molefractionofethanol\left(C_2{H}_{5}OH\right)=0.25=\frac{n_1}{n_1+n_2}$
$Molefractionofwater\left(H_{2}O\right)=0.75=\frac{n_2}{n_1+n_2}$
$\therefore \frac{n_1}{n_2}=\frac{0.25}{0.75}=\frac{1}{3}$
$C_2{H}_{5}OH=n_1=1mole=46g$
$H_{2}O=n_2=3moles=54g$
$Totalmass=46+54=100g$
Thus, it is $46\%$ ethanol by weight of solution and $54\%$ water by weight of solution.