Question

molar ionic conductivities of a divalent cation and anion are $57 \, \text{S cm}^2 \text{mol}^{-1}$ and $73 \, \text{S cm}^2 \text{mol}^{-1}$, respectively. The molar conductivity of the solution of an electrolyte with the above cation and anion will be:

• A. $65 \, \text{S cm}^2 \text{mol}^{-1}$
• B. $130 \, \text{S cm}^2 \text{mol}^{-1}$
• C. $187 \, \text{S cm}^2 \text{mol}^{-1}$
• D. $260 \, \text{S cm}^2 \text{mol}^{-1}$

Answer 1

Answer: (B)

$130 \, \text{S cm}^2 \text{mol}^{-1}$

Answer 2

The molar conductivity of a solution (ΛSolution) is given by the sum of molar ionic conductivities:

Λ+2C = 57 S cm2 mol-1
Λ+2A = 73 S cm2 mol-1

ΛSolution = λ+ + λ-
ΛSolution = 57 + 73 = 130 S cm2 mol-1