Select correct statement for `Cr. 6NH_3.Cl_3 and Cr.5NH_3.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 statements for `Cr. 6NH3.Cl3` and `Cr. 5NH3.Cl3`, we will analyze the complexes step by step.

### Step 1: Identify the complexes
The given complexes are:
1. `Cr(NH3)6Cl3` - This indicates that there are 6 ammonia (NH3) ligands and 3 chloride (Cl) ions.
2. `Cr(NH3)5Cl3` - This indicates that there are 5 ammonia (NH3) ligands and 3 chloride (Cl) ions.

### Step 2: Determine the coordination number and geometry
- For `Cr(NH3)6Cl3`, the coordination number is 6 (from 6 NH3 ligands), and this complex typically adopts an octahedral geometry.
- For `Cr(NH3)5Cl3`, the coordination number is also 6 (5 NH3 ligands and 1 Cl ligand), which can also lead to an octahedral geometry, but with different ligand arrangements.

### Step 3: Analyze primary and secondary valency
- **Primary valency** refers to the charge balance of the complex. In `Cr(NH3)6Cl3`, the primary valency is satisfied by the 3 chloride ions (Cl^-), which provide a -3 charge to balance the +3 charge of Cr. In `Cr(NH3)5Cl3`, the primary valency is also satisfied by the 3 chloride ions.
- **Secondary valency** refers to the number of ligands attached to the metal ion. In both complexes, the secondary valency is satisfied by the ammonia ligands.

### Step 4: Evaluate the statements
1. **Both complexes' secondary valency is satisfied only by ammonia.** - This is incorrect for `Cr(NH3)5Cl3` since Cl also contributes to the secondary valency.
2. **In both complexes, chloride ions satisfy only primary valency.** - This is incorrect as in `Cr(NH3)5Cl3`, Cl contributes to both primary and secondary valency.
3. **In both complexes, primary valency is satisfied only by chlorine.** - This is correct; both complexes use Cl to satisfy the primary valency.
4. **In both complexes, chlorides are ionizable.** - This is incorrect; in `Cr(NH3)5Cl3`, the Cl is part of the coordination sphere and is not ionizable.

### Conclusion
The correct statement is that in both complexes, primary valency is satisfied only by chlorine.