Question

A $5.2$ molal aqueous solution of methyl alcohol, $C{H}_{3}OH$ is supplied. What is the mole fraction of methyl alcohol in the solution?

• A. $0.05$
• B. $0.10$
• C. $0.18$
• D. $0.086$

Answer 1

The correct option is D $0.086$

A $5.2$ molal aqueous solution of methyl alcohol means that 1 kg ( or 1000 g) of water contains 5.2 moles of methyl alcohol. The molecular weight of water is 18 g/mol.

The number of moles of water
$=\frac{\text{1000 g}}{\text{18 g/mol}}=\text{55.56 mol}$

The mole fraction of methyl alcohol $=\frac{\text{5.2 mol}}{\text{5.2 mol}+\text{55.56 mol}}=\text{0.086}$.

Hence, the correct option is $D$