Question

2 M aqueous solution of a compound with a molar mass of 250 gm/mol and density 1.5 kg/L is given. Pick the incorrect option:

• A. Molality of the solution is 2 m
• B. Solution is 33.33% by mass
• C. Solution is 50% mass by volume
• D. Mole fraction of the solute is 0.05

Answer 1

The correct option is D Mole fraction of the solute is 0.05

$m=\frac{M\times 1000}{1000d-M\times M_{w}solute}=\frac{2\times 1000}{1000\times 1.5-2\times 250}=2m$

% by mass $=\frac{M\times M_{solute}}{1000\times d}\times 100=\frac{2\times 250}{1000\times 1.5}\times 100=\frac{1}{3}\times 100=33.33\%$

% mass by volume$=\frac{M\times M_{solute}}{1000}\times 100=\frac{2\times 250}{1000}\times 100=50\%$

1 L of the solution has 500 g (2 mol) solute and 1000 g water (55.56 mol). Mole fraction of the solute: $\frac{2}{57.56}=0.035$