Question

The molar conductivities at infinite dilution of barium chloride, sulphuric acid and hydrochloric acid are 280, 860 and 426 S cm² mol⁻¹ respectively. The molar conductivity at infinite dilution of barium sulphate is ________ S cm² mol⁻¹. (Round off to the Nearest Integer).

Hint:

Kohlrausch's Law allows us to calculate $\Lambda^\circ$ for weak electrolytes or insoluble salts using strong electrolytes.

Answer 1

Correct Answer: 288

Step 1: $\Lambda^\circ_{BaSO_4} = \Lambda^\circ_{BaCl_2} + \Lambda^\circ_{H_2SO_4} - 2\Lambda^\circ_{HCl}$.
Step 2: $\Lambda^\circ = 280 + 860 - 2(426) = 1140 - 852 = 288 \text{ S cm}^2 \text{ mol}^{-1}$.