Select correct statement for `Cr. 6NH_3.Cl_3 and Cr.5NH_2.Cl_3`

Options

A. In both complex compounds secondary valency is satisfied by only `NH_3`
B. In both complex compounds `Cl^(-)` are satisfying only primary valency
C. In both complex compounds primary valency is satisfied by only `Cl^(-)`
D. In both complex compounds all `Cl^-` are ionizable

Answer

To solve the question regarding the correct statement for the complexes Cr. 6NH3.Cl3 and Cr. 5NH3.Cl3, we will analyze the valencies and the roles of the ligands involved in both complexes.

### Step-by-Step Solution:

1. **Identify the Complexes:**
- We have two complexes:
- **Complex 1:** Cr. 6NH3.Cl3
- **Complex 2:** Cr. 5NH3.Cl3

2. **Determine the Charges:**
- For **Complex 1 (Cr. 6NH3.Cl3)**:
- The ammonia (NH3) is a neutral ligand, so it does not contribute to the charge.
- The three chloride ions (Cl-) contribute a total charge of -3.
- Therefore, the oxidation state of chromium (Cr) in this complex must be +3 to balance the -3 charge from Cl-.
- For **Complex 2 (Cr. 5NH3.Cl3)**:
- Again, NH3 is neutral, and the three Cl- contribute -3.
- However, in this case, the complex is Cr. 5NH3 with 3 Cl-, indicating that the oxidation state of chromium is +2 to balance the -3 charge from Cl-.

3. **Define Primary and Secondary Valency:**
- **Primary Valency:** This refers to the charge on the metal ion, which is balanced by the anions in the complex.
- **Secondary Valency:** This refers to the number of ligands attached to the metal ion.

4. **Analyze Each Statement:**
- **Statement 1:** In both complexes, secondary valency is satisfied only by NH3.
- **Analysis:** This is incorrect for Complex 2, as Cl- also contributes to the secondary valency.
- **Statement 2:** In both complexes, Cl- satisfies only primary valency.
- **Analysis:** This is incorrect for Complex 2, as Cl- also satisfies secondary valency.
- **Statement 3:** In both complexes, primary valency is satisfied by only Cl-.
- **Analysis:** This is correct. In both complexes, the negative charge is balanced solely by the Cl- ions.
- **Statement 4:** In both complexes, all Cl- ions are ionizable.
- **Analysis:** This is incorrect for Complex 2, as one Cl- is bonded to the metal and is not ionizable.

5. **Conclusion:**
- The only correct statement is **Statement 3**: In both the complex compounds, primary valency is satisfied by only Cl-.

### Final Answer:
The correct statement is **Option 3**: In both the complex compounds, primary valency is satisfied by only Cl-.