The molar conductivity of a 0.010 mol dm^-3 solution of propanoic acid, C₂H₅COOH, has been measured to be 2.25 mS m² mol^-¹ at 298 K. The ionic conductivity of hydronium, H₃O⁺, ions is 34.96 mS m² mol^-¹and of propanoate, C₂H₅COO^-, ions is 26.3 mS m² mol^-¹ at this temperature. Determine the acid dissociation constant of propanoic acid at 298 K.

Question

Quizplus · Accepted Answer

The degree of dissociation (α) is calculated using the formula: α = Λ / Λ∞, where Λ is the molar conductivity of the solution and Λ∞ is the molar conductivity at infinite dilution. Λ∞ can be calculated as the sum of the ionic conductivities of H3O+ and C2H5COO- ions. Using these values, the degree of dissociation is found, and then the acid dissociation constant (Ka) is calculated using the formula: Ka = cα² / (1-α), where c is the concentration of the acid. The calculation gives Ka ≈ 1.35 × 10^-5.

The Molar Conductivity of a 0