The limiting ionic molar conductivities of K⁺ and Cl⁻ in aqueous solution are 73.5 , S ,cm² ,mol⁻¹ and 76.5 , S ,cm² ,mol⁻¹ , respectively. The molar conductivity of a 0.04 , M KCl solution is found to be 142 , S ,cm² ,mol⁻¹ . The value of the Debye-Hückel-Onsager constant A for this solution is _ _ _ _ _ _ , S ,cm² ,mol⁻¹/(mol ,L⁻¹)^ 1/2 .

Step-by-step solution

First, we use Kohlrausch's law of independent migration of ions to find the limiting molar conductivity ( _ m ^ ) of KCl : _ m ^ ( KCl ) = _ m ^ ( K⁺ ) + _ m ^ ( Cl⁻ ) _ m ^ ( KCl ) = 73.5 + 76.5 = 150 , S ,cm² ,mol⁻¹ Next, we apply the Debye-Hückel-Onsager equation: _ m = _ m ^ - A c Given data for the solution: _ m = 142 , S ,cm² ,mol⁻¹ c = 0.04 , mol ,L⁻¹ c = 0.04 = 0.2 ,( mol ,L⁻¹ )^ 1/2 Substitute the values into the equation: 142 = 150 - A(0.2) A(0.2) = 150 - 142 A(0.2) = 8 A = 8 0.2 = 40 , S ,cm² ,mol⁻¹/(mol