Question

Arrange the following complexes in the increasing order of conductivity of their solution: \[ [\text{Cr(NH}_3\text{)}_5\text{Cl}] \text{Cl}_2, \, [\text{Cr(NH}_3\text{)}_3\text{Cl}_3], \, [\text{Cr(NH}_3\text{)}_6\text{Cl}_3] \]

Answer 1

The conductivity of a compound in solution depends on the number of ions it dissociates into. The greater the number of ions released when the compound dissociates, the higher the conductivity of the solution.

• [Cr(NH₃)₅Cl]Cl₂ dissociates into 2 ions: one of the ions is [Cr(NH₃)₅Cl] and the other is Cl^-.
• [Cr(NH₃)₃Cl₃] dissociates into 4 ions: [Cr(NH₃)₃Cl₃] dissociates into 1 ion of [Cr(NH₃)₃Cl₃] and 3 ions of Cl^-.
• [Cr(NH₃)₆Cl₃] dissociates into 6 ions: [Cr(NH₃)₆Cl₃] dissociates into 1 ion of [Cr(NH₃)₆Cl₃] and 3 ions of Cl^-.

Order of conductivity:

Since conductivity increases with the number of ions dissociated, the order of conductivity based on the dissociation into ions is:

[Cr(NH₃)₃Cl₃] < [Cr(NH₃)₅Cl]Cl₂ < [Cr(NH₃)₆Cl₃]