An aqueous solution of salt contains \(20 g\) of \(NaCl\) per liter. The pressure of the solution at \(35^oC\) will be
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 17.29 atm
Osmotic pressure of an electrolyte solution is given by the van’t Hoff equation \( \pi = iCRT \). NaCl is a strong electrolyte and dissociates completely, \( \ce{NaCl -> Na+ + Cl-} \), so i = 2.
\( \displaystyle C = \frac{20\ \text{g}}{58.5\ \text{g mol}^{-1} \times 1\ \text{L}} = 0.342\ \text{mol L}^{-1} \)
T = 35 + 273 = 308 K, R = 0.0821 L atm K−1 mol−1
\( \pi = 2 \times 0.342 \times 0.0821 \times 308 \approx 17.29\ \text{atm} \)
The osmotic pressure of the solution is 17.29 atm.
NCERT (2026-27 edition):
Osmosis and Osmotic Pressure – …
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 09-06 S3 31-05 S2 | – |