Question

Osmotic pressure of solution containing 0.15 gmol NaCl/1000 g H\(_2\)O at 25°C. Assume density of water as 997.0 kg/m\(^3\).

• A. \(\sim 3.7\) bar
• B. \(\sim 7.41\) bar
• C. \(\sim 5.3\) bar
• D. \(\sim 6.0\) bar

Hint:

Osmotic pressure: \(\pi = iCRT\).
NaCl has i = 2.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Osmotic pressure is calculated using the van't Hoff equation.
It depends on concentration, temperature, and the van't Hoff factor.

Step 2: Key Formula or Approach:
\(\pi = i \times C \times R \times T\).

Step 3: Detailed Explanation:
NaCl dissociates into Na\(^+\) and Cl\(^-\), so i = 2.
Concentration = 0.15 mol/kg water.
Assuming density of water = 997 kg/m\(^3\), volume of 1 kg water = 1/997 m\(^3\).
Molarity = 0.15 (1/997) = 0.15 \(\times\) 997 = 149.55 mol/m\(^3\).
R = 8.314 J/mol·K, T = 298 K.
\(\pi\) = 2 \(\times\) 149.55 \(\times\) 8.314 \(\times\) 298 = 741,000 Pa = 7.41 bar.
Thus, the osmotic pressure is \(\sim 7.41\) bar.

Step 4: Final Answer:
The osmotic pressure is approximately 7.41 bar.
Hence, the correct option is (B).