Question

At \( 27^\circ \text{C} \), 0.1 M, 1 L \( K_4[Fe(CN)_6] \) aqueous solution and 0.1 M, 1 L \( FeCl_3 \) aqueous solution are placed in a container separated by a semi permeable membrane AB. Assume complete dissociation of both the solutes. Which of the following statement is correct?

• A. Blue color is formed on both sides.
• B. Ionic solutes in aqueous solution can pass through semi-permeable membrane.
• C. Solution on side 'y' is hypotonic.
• D. To cause the reverse flow of solvent during osmosis, external pressure (any value) should be applied to side 'x'.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Osmotic pressure depends on the total concentration of dissolved particles (osmolarity). A semi-permeable membrane allows solvent (water) to pass but blocks solute particles (ions). Hypotonic solutions have lower particle concentration compared to another.

Step 2: Key Formula or Approach:
1. Van't Hoff factor \( i \) = total ions produced upon dissociation.
2. Osmotic concentration = \( i \times M \).

Step 3: Detailed Explanation:
Side 'x' (\( K_4[Fe(CN)_6] \)): Dissociates into \( 4K^+ + [Fe(CN)_6]^{4-} \). Thus, \( i = 5 \).
Conc\(_x = 5 \times 0.1 = 0.5 \text{ M} \).
Side 'y' (\( FeCl_3 \)): Dissociates into \( Fe^{3+} + 3Cl^- \). Thus, \( i = 4 \).
Conc\(_y = 4 \times 0.1 = 0.4 \text{ M} \).
- (A) False: Ions don't pass membrane; Prussian blue reaction cannot happen.
- (B) False: Definition of semi-permeable membrane is that solutes cannot pass.
- (C) True: Side 'y' has lower osmolarity (\( 0.4<0.5 \)), so it is hypotonic.
- (D) False: To stop or reverse osmosis, a specific minimum pressure (osmotic pressure difference) must be applied, not "any value".

Step 4: Final Answer:
Statement (C) is correct.