Paper: CSIR-NET December 2018 · Subject: Physical Chemistry · Chapter: Electrochemistry · Topic: Electrochemistry – General · Marks: 2 · Difficulty: Medium
Conductivities of water and a saturated solution of a sparingly soluble salt $\mathrm{AB_2}$ are $7$ and $21\,\mu\mathrm{S\,m^{-1}}$, respectively. Given, $\lambda^{o}_{A^{2+}}=12.72\,\mathrm{mS\,m^{2}\,mol^{-1}}$ and $\lambda^{o}_{B^{2-}}=7.64\,\mathrm{mS\,m^{2}\,mol^{-1}}$, the solubility of $\mathrm{AB_2}$, in $\mathrm{mol\,m^{-3}}$, is
(a)$5.0 \times 10^{-4}$
(b)$5.0 \times 10^{-3}$
(c)$5.0 \times 10^{-5}$
(d)$5.0 \times 10^{-6}$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
κ(salt) = 21 − 7 = 14 µS m⁻¹ = 1.4 × 10⁻⁵ S m⁻¹. Λ° = 12.72 + 2 × 7.64 = 28.0 mS m² mol⁻¹. s = κ/Λ° = 5.0 × 10⁻⁴ mol m⁻³ (a).