Question

Out of the following complex compounds, which of the compound will be having the minimum conductance in solution?

• A. \([Co(NH_3)_4Cl_2]Cl\)
• B. \([Co(NH_3)_6]Cl_3\)
• C. \([Co(NH_3)_5Cl]Cl\)
• D. \([Co(NH_3)_3Cl_3]\)

Hint:

For complex compounds, the conductance is directly related to the number of ions produced during dissociation. Neutral complexes have the minimum conductance.

Answer 1

The Correct Option is D

The conductance of a solution depends on the number of ions present in the solution. When coordination complexes dissolve in water, the counter-ions dissociate, contributing to the conductance. Ligands inside the coordination sphere do not dissociate.

Let's analyze each complex:

1. $[Co(NH_3)_4Cl_2]Cl$ dissociates into $[Co(NH_3)_4Cl_2]^+$ and $Cl^-$. This gives 2 ions in solution.

2. $[Co(NH_3)_6]Cl_3$ dissociates into $[Co(NH_3)_6]^{3+}$ and $3Cl^-$. This gives 4 ions in solution.

3. $[Co(NH_3)_5Cl]Cl_2$ dissociates into $[Co(NH_3)_5Cl]^{2+}$ and $2Cl^-$. This gives 3 ions in solution.

4. $[Co(NH_3)_3Cl_3]$ does not have any counter-ions outside the coordination sphere.
Therefore, it does not dissociate into any ions in solution. It exists as a neutral molecule in solution.
Therefore, this is not an electrolyte, and has minimum conductance.

Therefore, the complex with the minimum conductance will be the one that produces the fewest ions in solution.

Thus, the compound with the minimum conductance is $[Co(NH_3)_3Cl_3]$.