Which of the following complex compound is ''Pentaaquacyanidoiron (III) trichloridotricyanido cobaltate (III) '' ?

Options

A. `[Fe(CN)(H_2O)_5][CoCl_3(CN)_3]`
B. `[Fe(CN)(H_2O)_5][CoCl_3(CN)_3]_3`
C. `[Fe(CN)(H_2O)_4]_3[CoCl_3(CN)_3]_2`
D. `[Fe(CN)(H_2O)_5]_3[CoCl_3(CN)_3]_2`

Answer

To determine the formula of the complex compound "Pentaaquacyanidoiron (III) trichloridotricyanido cobaltate (III)", we will break down the name into its components and systematically construct the formula.

### Step-by-Step Solution:

1. **Identify the Central Metal Ions**:
- The name indicates two central metal ions: Iron (Fe) and Cobalt (Co).
- Iron is in the +3 oxidation state (indicated by (III)).
- Cobalt is also in the +3 oxidation state (indicated by (III)).

2. **Identify the Ligands**:
- The term "Pentaaqua" indicates there are five water ligands (H₂O).
- The term "cyanido" indicates there is one cyanide ligand (CN⁻).
- The term "trichlorido" indicates there are three chloride ligands (Cl⁻).
- The term "tricyanido" indicates there are three cyanide ligands (CN⁻).

3. **Construct the Formula**:
- Start with the iron complex:
- Iron (III) with five water ligands and one cyanide ligand gives us:
\[ \text{[Fe(CN)(H}_2\text{O)}_5]^{3+} \]
- Now, consider the cobalt complex:
- Cobalt (III) with three chloride ligands and three cyanide ligands gives us:
\[ \text{[CoCl}_3\text{(CN)}_3]^{3-} \]

4. **Combine the Complexes**:
- The overall formula combines the iron complex with the cobalt complex:
- Therefore, the complete formula becomes:
\[ \text{[Fe(CN)(H}_2\text{O)}_5][CoCl_3(CN)_3] \]

5. **Final Formula**:
- The final formula can be simplified to:
\[ \text{[Fe(H}_2\text{O)}_5\text{CN][CoCl}_3\text{(CN)}_3} \]

### Conclusion:
The correct formula for the complex compound "Pentaaquacyanidoiron (III) trichloridotricyanido cobaltate (III)" is:
\[ \text{[Fe(H}_2\text{O)}_5\text{CN][CoCl}_3\text{(CN)}_3} \]