Question

Which of the following aqueous solutions has the highest osmotic pressure?

• A. 5.85\% NaCl
• B. 3.42\% \( \text{Al}_2(\text{SO}_4)_3 \)
• C. 6\% Urea
• D. 18\% Glucose

Hint:

Osmotic pressure increases with the number of particles in solution. Electrolytes like NaCl dissociate into more particles, which increases the osmotic pressure.

Answer 1

The Correct Option is A

The osmotic pressure \( \Pi \) is given by the formula: \[ \Pi = i \cdot M \cdot R \cdot T \] Where: - \( i \) is the van 't Hoff factor (the number of particles the solute dissociates into),
- \( M \) is the molarity,
- \( R \) is the ideal gas constant,
- \( T \) is the temperature.
For NaCl, it dissociates into two ions, Na\(^+\) and Cl\(^-\), thus \( i = 2 \).
For \( \text{Al}_2(\text{SO}_4)_3 \), it dissociates into 5 ions, thus \( i = 5 \).
For urea and glucose, both are non-electrolytes and do not dissociate into ions, so \( i = 1 \).
Therefore, even though \( \text{Al}_2(\text{SO}_4)_3 \) dissociates into more ions, the concentration and dissociation factor need to be considered in detail. The osmotic pressure is determined by both the concentration and dissociation factor, and the 5.85% NaCl solution gives the highest osmotic pressure among the options.