Given the molecular formula of the hexacoordinated complexes (A) `[CoCl_(3).6NH_3]` (B) `[CoCl_(3).5NH_3]` (C) `CoCl_(3).4NH_3`. If the number of coordinated `NH_3` molecules in A, B and C respectively are 6, 5 and 4, the primary valency in (A), (B) and (C) are:

Options

A. 3, 3, 3
B. 0, 1, 2
C. 3, 2, 1
D. 6, 5, 4

Answer

To determine the primary valency of the hexacoordinated complexes (A), (B), and (C), we need to analyze each complex based on the number of coordinated NH3 molecules and the chloride ions present.

### Step-by-Step Solution:

1. **Identify the Complexes:**
- Complex A: \[CoCl_3 \cdot 6NH_3\]
- Complex B: \[CoCl_3 \cdot 5NH_3\]
- Complex C: \[CoCl_3 \cdot 4NH_3\]

2. **Determine the Coordination Number:**
- For complex A, the coordination number is 6 (from 6 NH3).
- For complex B, the coordination number is 5 (from 5 NH3).
- For complex C, the coordination number is 4 (from 4 NH3).

3. **Determine the Charge on the Coordination Sphere:**
- **Complex A:**
- The cobalt ion (Co) is in the +3 oxidation state (since it is combined with 3 chloride ions).
- The complex can be represented as \[Co(NH_3)_6^{3+}\] with 3 Cl^- ions outside.
- Therefore, the primary valency (oxidation state) is +3.

- **Complex B:**
- The cobalt ion (Co) is in the +2 oxidation state (since it is combined with 2 chloride ions).
- The complex can be represented as \[Co(NH_3)_5Cl^{2+}\] with 2 Cl^- ions outside.
- Therefore, the primary valency is +2.

- **Complex C:**
- The cobalt ion (Co) is in the +1 oxidation state (since it is combined with 1 chloride ion).
- The complex can be represented as \[Co(NH_3)_4Cl^{+}\] with 1 Cl^- ion outside.
- Therefore, the primary valency is +1.

4. **Summarize the Results:**
- For complex A: Primary valency = +3
- For complex B: Primary valency = +2
- For complex C: Primary valency = +1

### Final Answer:
- The primary valencies for complexes A, B, and C are +3, +2, and +1 respectively.