0.01 molal aqueous solutions of strong electrolytes \(NaCl\), \(KCl\), \(MgSO_4\) and \(K_2SO_4\) are prepared. Which of the following statements is correct regarding their osmotic pressure? (Assume complete dissociation of solute particles)

\(K_2SO_4\) has highest osmotic pressure

The correct answer is option 4. \(K_2SO_4\) has highest osmotic pressure.

To determine the osmotic pressure of 0.01 molal aqueous solutions of the strong electrolytes \( \text{NaCl} \), \( \text{KCl} \), \( \text{MgSO}_4 \), and \( \text{K}_2\text{SO}_4 \), we need to consider the van 't Hoff factor (\(i\)), which represents the number of particles the solute dissociates into in solution.

The osmotic pressure (\( \pi \)) is given by the formula:

\(\pi = iCRT \)

where:

\( i \) is the van 't Hoff factor,

\( C \) is the molality of the solution,

\( R \) is the gas constant,

\( T \) is the temperature in Kelvin.

Determining the van 't Hoff Factor for Each Electrolyte

\( \text{NaCl} \) (Sodium chloride):

Dissociates into \( \text{Na}^+ \) and \( \text{Cl}^- \).

van 't Hoff factor \( i = 2 \).

\( \text{KCl} \) (Potassium chloride):

Dissociates into \( \text{K}^+ \) and \( \text{Cl}^- \).

van 't Hoff factor \( i = 2 \).

\( \text{MgSO}_4 \) (Magnesium sulfate):

Dissociates into \( \text{Mg}^{2+} \) and \( \text{SO}_4^{2-} \).

van 't Hoff factor \( i = 2 \) (Note: In dilute solutions, the ion pairing is negligible, so \( i = 2 \)).

\( \text{K}_2\text{SO}_4 \) (Potassium sulfate):

Dissociates into 2 \( \text{K}^+ \) and 1 \( \text{SO}_4^{2-} \).

van 't Hoff factor \( i = 3 \).

Osmotic Pressure Calculation

For equal molal solutions (0.01 molal) and the same temperature, the osmotic pressure will depend on the van 't Hoff factor:

\( \text{NaCl} \): \( \pi = i \cdot C = 2 \cdot 0.01 \)

\( \text{KCl} \): \( \pi = i \cdot C = 2 \cdot 0.01 \)

\( \text{MgSO}_4 \): \( \pi = i \cdot C = 2 \cdot 0.01 \)

( \text{K}_2\text{SO}_4 \): \( \pi = i \cdot C = 3 \cdot 0.01 \)

Conclusion:

The osmotic pressure of \( \text{K}_2\text{SO}_4 \) will be the highest due to its highest van 't Hoff factor. Thus, the correct statement is: (4) \( \text{K}_2\text{SO}_4 \) has highest osmotic pressure.