A solution of KCl ( M =74.5 ~g ~mol ⁻¹) containing 1.9 ~g per 100 ~mL of KCl is isotonic with a solution of urea ( M =60.0 ~g ~mol ⁻¹ ) containing 3 ~g per 100 ~mL of urea. The degree of dissociation of KCl is: [Assume both the solutions are kept at same temperature]

Step-by-step solution

For two isotonic solutions at the same temperature, the osmotic pressures are equal, which implies their molar concentrations are equal when accounting for the van't Hoff factor i . The molar concentration of the KCl solution is C₁ = 1.9 g / 74.5 g mol ⁻¹ 0.1 L = 1.9 7.45 M 0.255 M . The molar concentration of the urea solution is C₂ = 3 g / 60.0 g mol ⁻¹ 0.1 L = 3 6 M = 0.5 M . Since urea is a non-electrolyte, its van't Hoff factor i₂ = 1 . For KCl, which dissociates as KCl K ⁺ + Cl ⁻ , the van't Hoff factor is i₁