Question

1.26 g of a solid was dissolved in 200 cm\(^3\) aqueous solution. The osmotic pressure of the solution at 300 K was found to be \( 2.57 \times 10^{-3} \) bar. Calculate the molar mass of the solid.

Hint:

Use osmotic pressure to determine the molecular mass of polymers and macromolecules.

Answer 1

Step 1: Given Data \[ w = 1.26g, \quad V = 200cm^3 = 0.2L, \quad T = 300K, \quad \pi = 2.57 \times 10^{-3} \text{ bar}, \quad R = 0.0831 \text{ L bar mol}^{-1}K^{-1} \] Step 2: Using Osmotic Pressure Formula \[ M = \frac{wRT}{\pi V} \] Step 3: Substituting Values \[ M = \frac{1.26 \times 0.0831 \times 300}{(2.57 \times 10^{-3}) \times 0.2} \] \[ M = \frac{31.41}{0.000514} = 61.1 \text{ g mol}^{-1} \]