Question

Imagine you had prepared a 0.1 M sodium sulfate solution. Would you expect it to have a conductivity value that was the same, higher than or lower than the 0.1 M sodium chloride solution? Explain your answer.

Answer 1

conductivity of a salt solution depends on two factors:

1. No of ions

2. Mobility of ions

No of ions in NaCl solution is lower than the no of ions in a Na₂SO₄ ions, because dissociation of NaCl gives Na+ and Cl- , while dissociation of Na₂SO₄ gives two Na+ and one SO₄^2- ion.

As total no of ions in Na₂SO₄ is greater than Solution of NaCl, so conductance of 0.1 M Na₂SO₄ solution

will be greater than 0.1 M NaCl.

Moreover conductance of So₄^2- is greater than Cl-.

λ_-⁰ /mS m²mol⁻¹ of Cl- = 7.634

λ_-⁰ /mS m²mol⁻¹ of SO₄^2- = 15.96

Conductance of 0.1 M Na₂SO₄ solution will be greater than 0.1 M NaCl.