Which of the following complex compound is ''Pentaaqucyanidoiron (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)_2(H_2O)_4]_3[FeCl_3(cN)_3]_2`
D. `[Fe(CN)(H_2O)_5]_3[CoCl_3(CN)_3]_2`

Answer

To determine the formula for the complex compound "Pentaaquacyanidoiron (III) trichloridotricyanidocobaltate (III)", we will break down the name into its cationic and anionic parts and analyze them step by step.

### Step-by-Step Solution:

1. **Identify the Cationic Part:**
- The cationic part is "Pentaaquacyanidoiron (III)".
- "Iron (III)" indicates that iron (Fe) is the central atom with a +3 oxidation state (Fe³⁺).
- "Penta" means there are 5 water molecules (H₂O), so we have 5 H₂O.
- "Cyanido" refers to the cyanide ion (CN⁻), and since there is no prefix before "cyanido", it indicates there is 1 cyanide ion.

**Cationic Formula:**
\[ \text{Cation} = \text{Fe}^{3+} + 5 \text{H}_2\text{O} + \text{CN}^- \]
Therefore, the cationic part can be represented as:
\[ \text{[Fe(H}_2\text{O})_5\text{CN}]^{2+} \]

2. **Identify the Anionic Part:**
- The anionic part is "Trichloridotricyanidocobaltate (III)".
- "Cobaltate (III)" indicates that cobalt (Co) is the central atom with a +3 oxidation state (Co³⁺).
- "Trichlorido" means there are 3 chloride ions (Cl⁻).
- "Tricyanido" means there are 3 cyanide ions (CN⁻).

**Anionic Formula:**
\[ \text{Anion} = \text{Co}^{3+} + 3 \text{Cl}^- + 3 \text{CN}^- \]
Therefore, the anionic part can be represented as:
\[ \text{[CoCl}_3\text{(CN)}_3]^{3-} \]

3. **Combine the Cationic and Anionic Parts:**
- The overall complex compound will combine the cation and anion.
- The charges must balance: the cation has a +2 charge and the anion has a -3 charge.
- To balance the charges, we need 3 of the anionic part for every 2 of the cationic part.

**Final Complex Formula:**
\[ \text{[Fe(H}_2\text{O})_5\text{CN}]^{2+} \text{ and } 3 \text{[CoCl}_3\text{(CN)}_3]^{3-} \]
Therefore, the final formula for the complex compound is:
\[ \text{[Fe(H}_2\text{O})_5\text{CN]}_2\text{[CoCl}_3\text{(CN)}_3]_3 \]

### Final Answer:
The complex compound is represented as:
\[ \text{[Fe(H}_2\text{O})_5\text{CN]}_2\text{[CoCl}_3\text{(CN)}_3]_3 \]