Question: 63. Out of the following complex compounds, which of the compound will be having the minimum conductance is solution?
(1) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]
(2) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}
(3) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}
(4) All have same minimum
Answer: Option (1)
Explanation:
The conductance of a coordination compound in solution depends on the number of ions it produces on dissociation.
A compound that does not ionize or produces the least number of ions in solution will have minimum conductance.
Consider each complex:
(1) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]
All three chloride ligands are coordinated to cobalt and are inside the coordination sphere.
This compound does not ionize in solution.
Number of ions produced = 0.
(2) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}
All three chloride ions are present outside the coordination sphere.
On dissociation:
\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+} + 3 \mathrm{Cl}^-Total ions = 4.
(3) \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}
One chloride is inside and one chloride is outside the coordination sphere.
On dissociation:
\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^+ + \mathrm{Cl}^-Total ions = 2.
Since option (1) do not ionize and produce zero ions, it has the minimum conductance in solution.