Based upon the technique of reverse osmosis, the approximate minimum pressure required to desalinate — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

2.5% (w/v) NaCl means 25 g of NaCl in 1 L. Molarity $= 25 / 58.5 = 0.427$ M. Temperature $= 27^\circ C = 300$ K. NaCl dissociates into 2 ions ($i=2$). Osmotic pressure $\pi = iCRT = 2 \times 0.427 \times 0.0821 \times 300 \approx 21.03$ atm. A minimum pressure of 21 atm is required to overcome the osmotic pressure. Therefore, correct answer is B.