Question

The mole fraction of ethanol in water is 0.65. Calculate its molality.

• A. 55.5 m
• B. 5.55 m
• C. 27.8 m
• D. 2.78 m

Answer 1

The correct option is B 5.55 m

Assuming the total number of moles to be 1,
Moles of ethanol = 0.65 mol
Moles of water = 0.35 mol
Mass of water = $0.35\times 18=6.3g$
Molality of ethanol = $\frac{\text{Moles of the solute}}{\text{Mass of the solvent in kg}}=\frac{0.35}{0.0063}=55.5\text{m}$