Question

The mole fraction of a solute in 2.0 molal aqueous solution is :

• A. 1.87
• B. 0.347
• C. 0.0347
• D. 0.00347

Hint:

For a molal solution, always assume 1 kg solvent. In aqueous solutions, 1000 g water corresponds to approximately 55.56 moles of water.

Answer 1

The Correct Option is C

Step 1: Interpret molality.
2.0 molal means 2 mol solute per 1000 g water. Moles of water = $\frac{1000}{18}$ = 55.56 mol.
Step 2: Find total moles.
Total moles in solution = 2 + 55.56 = 57.56 mol.
Step 3: Compute mole fraction of solute.
$X_{\text{solute}} = \dfrac{2}{57.56} = 0.0347$
\[ \boxed{X_{\text{solute}} = 0.0347} \]