Question

The correct order of conductivity of 0.001 (M) separate aqueous solutions of \([\text{Pt}(\text{NH}_3)_6]\text{Cl}_4\) (i); \([\text{Cr}(\text{NH}_3)_6]\text{Cl}_3\) (ii); \([\text{Co}(\text{NH}_3)_4\text{Cl}_2]\text{Cl}\) (iii) and \(\text{K}_2\text{PtCl}_6\) (iv) each containing octahedral complex species is

• A. (i) $<$ (ii) $<$ (iii) $<$ (iv)
• B. (i) $<$ (ii) $<$ (iv) $<$ (iii)
• C. (i) $<$ (iv) $<$ (iii) $<$ (ii)
• D. (iii) $<$ (iv) $<$ (ii) $<$ (i)

Hint:

In coordination chemistry, the electrical conductivity of aqueous solutions is a direct measure of the number of charges/ions. Count the species outside the coordination sphere plus the complex sphere itself to determine the total ion count.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The molar conductivity of an electrolyte solution depends on the total number of ions produced per formula unit upon dissociation in water.


Step 2: Key Formula or Approach:
Greater number of ions in solution leads to higher electrical conductivity of the solution at a given concentration.
Let us determine the dissociation of each coordination compound in water.


Step 3: Detailed Explanation:
Let us write down the ionization reactions for each complex:
- (i) $[\text{Pt}(\text{NH}_3)_6]\text{Cl}_4 \rightarrow [\text{Pt}(\text{NH}_3)_6]^{4+} + 4\text{Cl}^-$
Total number of ions produced = $1 + 4 = 5$ ions.
- (ii) $[\text{Cr}(\text{NH}_3)_6]\text{Cl}_3 \rightarrow [\text{Cr}(\text{NH}_3)_6]^{3+} + 3\text{Cl}^-$
Total number of ions produced = $1 + 3 = 4$ ions.
- (iii) $[\text{Co}(\text{NH}_3)_4\text{Cl}_2]\text{Cl} \rightarrow [\text{Co}(\text{NH}_3)_4\text{Cl}_2]^+ + \text{Cl}^-$
Total number of ions produced = $1 + 1 = 2$ ions.
- (iv) $\text{K}_2\text{PtCl}_6 \rightarrow 2\text{K}^+ + [\text{PtCl}_6]^{2-}$
Total number of ions produced = $2 + 1 = 3$ ions.
Now, comparing the number of ions produced by each compound:
- (iii) produces 2 ions.
- (iv) produces 3 ions.
- (ii) produces 4 ions.
- (i) produces 5 ions.
Since conductivity is directly proportional to the number of ions, the order of conductivity is:
\[ (\text{iii}) < (\text{iv}) < (\text{ii}) < (\text{i}) \]


Step 4: Final Answer:
The correct option is (D).