Osmotic pressure of 0.02 M urea solution at 27 °C, is (given $R = 0.0821\, atm\, L\, mol^{-1}\, K^{-1}$)
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 0.4926 atm
Using the van't Hoff equation for osmotic pressure:
$\pi = iCRT$
Identify the variables:
- Concentration ($C$): $0.02\ \text{mol/L}$
- Gas Constant ($R$): $0.0821\ \text{L} \cdot \text{atm} / (\text{mol} \cdot \text{K})$
- Temperature ($T$): Convert from Celsius to Kelvin:
$T = 27\ ^\circ\text{C} + 273 = 300\ \text{K}$
- van't Hoff factor ($i$): For urea, which is a non-electrolyte, $i = 1$.
Substitute the values into the equation:
$\pi = (1) \times (0.02\ \text{mol/L}) \times \left(0.0821\ \frac{\text{L} \cdot \text{atm}}{\text{mol} \cdot \text{K}}\right) \times (300\ \text{K})$
Calculate the result:
$\pi = 0.4926\ \text{atm}$
The calculated osmotic pressure is $\mathbf{0.4926\ \text{atm}}$.