'x' grams of water are mixed with 69 g of ethanol. The mole fraction of ethanol in the resultant solution is 0.6. What is the value of 'x' in grams?

Mole fraction of water in solution$=1-0.6=0.4$
Number of moles of water in solution $=\mathrm{n}$

Moles of alcohol $=\frac{\text{ Given mass }}{\text{ molecular mass }}=\frac{69}{46}=\frac{3}{2}$

The mole fraction of water in the solution can also be expressed as: $\frac{\mathrm{n}}{\mathrm{n}+\frac{3}{2}}=0.4$

or, n =1

Therefore the correct option is D)18 as it is the molar mass of 1 mole of water.