Question

A solution containing 10g per d/m of urea( molecular mass=60g/mol) is isotonic with a 5%solution of non volatile solute. The molecular mass of this non volatile solute is

• A. 250
• B. 300
• C. 350
• D. 200

Answer 1

The correct option is B 300

Molar concentration of urea solution =$\frac{1}{6}$, as $10gperd/m$ of urea solution, molecular mass $=60g/mol$

Molar concentration of $5$% non - volatile solute

$=\frac{50g/d{m}^3}{Mol.weightofnon-volatilesolute}$

$=50\frac{M}{m}$

Both solutions are isotonic to each other, therefore,

$\frac{1}{6}=\frac{50}{m}$

$m=6\times 50=300$

Option B is correct.