Question

Solution of 12 g of non-electrolyte (A) prepared by dissolving it in 1000 mL of water exerts the same osmotic pressure as that of 0.05 M glucose solution at the same temperature. The empirical formula of A is CH₂O. The molecular mass of A is ____ g. (Nearest integer)

Answer 1

Correct Answer: 240

The osmotic pressure (\( \pi \)) for a solution is given by the formula:
\[ \pi = \frac{nRT}{V} \] where:

\( n \) is the number of moles of solute,

\( R \) is the gas constant,

\( T \) is the temperature,

\( V \) is the volume of the solution.

For non-electrolyte (A) and glucose, the osmotic pressures are the same, so we can equate the osmotic pressures: \[ \frac{12 / M_A}{1} = 0.05 \times 1 \] where \( M_A \) is the molar mass of A, and 12 g is the mass of A. Simplifying the equation: \[ \frac{12}{M_A} = 0.05 \quad \Rightarrow \quad M_A = \frac{12}{0.05} = 240 \, \text{g/mol}. \] Thus, the molecular mass of A is 240 g/mol.