Select the compound having maximum conductivity in aqueous medium.

Options

A. `[Cr(NH_3)_6]Cl_3`
B. `[Cr(NH_3)_5Cl]Cl_2`
C. `[Cr(NH_3)_4Cl_2]Cl`
D. `[Cr(NH_3)_3Cl_3]`

Answer

To determine which compound has maximum conductivity in an aqueous medium, we need to analyze the number of ions produced when each compound dissociates in water. Conductivity in an aqueous solution is directly proportional to the number of ions present.

### Step-by-Step Solution:

1. **Understand the Concept of Conductivity**:
- Conductivity in an aqueous medium depends on the number of ions present in the solution. More ions lead to higher conductivity.

2. **Analyze Each Compound**:
- **Compound 1**: Let's denote it as \( \text{[Cr(NH}_3\text{)}_3\text{Cl}_3] \).
- When this compound dissociates, it forms 1 complex ion and 3 chloride ions:
\[ \text{[Cr(NH}_3\text{)}_3\text{Cl}_3] \rightarrow \text{[Cr(NH}_3\text{)}_3]^+ + 3\text{Cl}^- \]
- Total ions = 1 (complex ion) + 3 (chloride ions) = 4 ions.

- **Compound 2**: Denote it as \( \text{[Cr(NH}_3\text{)}_5\text{Cl}] \text{Cl}_2 \).
- This will dissociate to form 1 complex ion and 2 chloride ions:
\[ \text{[Cr(NH}_3\text{)}_5\text{Cl}] \text{Cl}_2 \rightarrow \text{[Cr(NH}_3\text{)}_5]^+ + 2\text{Cl}^- \]
- Total ions = 1 (complex ion) + 2 (chloride ions) = 3 ions.

- **Compound 3**: Denote it as \( \text{[Cr(NH}_3\text{)}_4\text{Cl}_2] \text{Cl} \).
- This will dissociate to form 1 complex ion and 1 chloride ion:
\[ \text{[Cr(NH}_3\text{)}_4\text{Cl}_2] \text{Cl} \rightarrow \text{[Cr(NH}_3\text{)}_4]^+ + 2\text{Cl}^- \]
- Total ions = 1 (complex ion) + 2 (chloride ions) = 3 ions.

- **Compound 4**: Denote it as \( \text{[Cr(NH}_3\text{)}_6]^{3+} \).
- This is a neutral complex and does not dissociate:
\[ \text{[Cr(NH}_3\text{)}_6]^{3+} \rightarrow \text{[Cr(NH}_3\text{)}_6]^{3+} \]
- Total ions = 1 (the complex ion itself) = 1 ion.

3. **Compare the Total Number of Ions**:
- Compound 1: 4 ions
- Compound 2: 3 ions
- Compound 3: 3 ions
- Compound 4: 1 ion

4. **Conclusion**:
- The compound with the maximum number of ions is Compound 1, which has 4 ions. Therefore, it will have the highest conductivity in an aqueous medium.

### Final Answer:
The compound having maximum conductivity in aqueous medium is **Compound 1**.