Question

The mole fraction of the solute in one molal aqueous solution is:

• A. 0.054
• B. 0.042
• C. 0.018
• D. 0.009

Answer 1

Answer: (C)

0.018

Answer 2

Since the solution is one molal, the weight of the solvent water is 1 kg or 1000 g per mole of solute.
Additionally, g. mol. wt. of H2O = (21+1) + 16 = 18 g.
Therefore, no. of moles of H2O = 100018 = 55.5 and no. of moles of solute + no. of moles of H2O =$\frac{1 mol}{1mol+55.5 mol}$ = 0.018.

The correct option is (C): 0.018