Question

At 20°C the osmotic pressure of 45 gm per litre solution of a substance is 3.2 atmosphere. Calculate the value of solution constant. The molecular mass of the substance is 342.

Hint:

Osmotic pressure calculations use the formula \( \pi = CRT \). Ensure correct unit conversions for temperature and gas constant.

Answer 1

Step 1: The osmotic pressure (\( \pi \)) is related to molarity (\( C \)) using the formula: \[ \pi = CRT \] where \( R = 0.0821 \) L atm mol\(^{-1}\)K\(^{-1}\) and \( T = 293 \) K. Step 2: Molarity \( C \) is given by: \[ C = \frac{\text{mass of solute}}{\text{molar mass} \times \text{volume (L)}} \] Substituting values, \[ C = \frac{45}{342 \times 1} = 0.1316 \text{ mol/L} \] Step 3: Now, solving for \( C \), \[ 3.2 = (0.0821 \times 293) C \] \[ C = \frac{3.2}{0.0821 \times 293} = 0.1332 \text{ mol/L} \]