Question

$x$ grams of water is mixed with $69$ grams of ethanol. Mole fraction of ethanol in the resultant solution is $0.6$. What is the value of $x$ in grams?

• A. 54
• B. 36
• C. 180
• D. 18

Answer 1

Answer: (D)

Mole fraction of water in solution = $1-0.6=0.4$

Number of moles of water in solution = $n$

Moles of alcohol $=\frac{\text{Given mass}}{\text{molecular mass}}$

$=\frac{69}{46}$

$=\frac{3}{2}$

$\frac{n}{n+\frac{3}{2}}=0.4$

or, $n=1$

$\therefore$ Mass of water in solution = $18$ g.