Question

Why do the Group A compounds, each with the same concentration (0.05 M), have such large differences in conductivity values? Hint: Write an equation for the dissociation of each. Explain.

Answer 1

Conductivity of different compounds is different with same concentration when they give different number of ions on dissociation. Higher the number of ions produced higher is the conductivity.

The number of ions produced depends on the following factors:

(a)Ionic character:. Higher the ionic character higher is the number of ions produced. E.g. Between NaCl and AlCl3, NaCl, being more ionic gives higher number of ions when dissolved in water. Hence conductivity of NaCl is more than AlCl3.

(b) Extent of hydration: Higher is the extent of hydration, higher is the number of water molecules surrounded by the ion. This decreases the ionic mobility of the ion and hence conductivity decreases. E.g. Between CaCl2 and AlCl3, Al3+ has higher extent of hydration than Ca2+. Hence Al3+ has lower ionic mobility and hence lower ionic conductance.