Question

The ratio of osmotic pressures of aqueous solutions of 0.01 M BaCl₂ to 0.005 M NaCl is
[Given: Both compounds dissociate completely in water]

• A. 3:1
• B. 1:4
• C. 1:1
• D. 3:2

Answer 1

The Correct Option is A

Osmotic pressure (π) is directly proportional to the molar concentration of the solute and the number of ions produced when the solute dissociates.

• BaCl₂ dissociates into 3 ions (Ba²⁺, 2Cl⁻) per formula unit, so the effective concentration of ions is 0.01 × 3 = 0.03 M.
• NaCl dissociates into 2 ions (Na⁺, Cl⁻) per formula unit, so the effective concentration of ions is 0.005 × 2 = 0.01 M.

Therefore, the ratio of osmotic pressures is:

\( \frac{\text{osmotic pressure of BaCl}_2}{\text{osmotic pressure of NaCl}} = \frac{0.03}{0.01} = 3\)

Thus, the correct answer is (A). 3:1