Which of the following is the odd one out ?

Options

A. Potassium ferrocyanide
B. Tetramminezinc(II) chloride
C. Ferrous Ammonium Sulphate
D. Potasium Ferricyanide

Explanation

To determine which of the following options is the odd one out, we will analyze each option based on their chemical nature.

### Step 1: Identify the compounds
1. **Potassium Ferrocyanide**: The molecular formula is \( K_4[Fe(CN)_6] \).
2. **Tetraamminezinc(II) Chloride**: The molecular formula is \( Zn(NH_3)_4Cl_2 \).
3. **Ferrous Ammonium Sulfate**: The molecular formula is \( FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O \) (also known as Mohr's salt).
4. **Potassium Ferricyanide**: The molecular formula is \( K_3[Fe(CN)_6] \).

### Step 2: Classify the compounds
- **Potassium Ferrocyanide** and **Potassium Ferricyanide** are coordination compounds because they contain a central metal ion (Fe) surrounded by ligands (CN).
- **Tetraamminezinc(II) Chloride** is also a coordination compound as it has a central metal ion (Zn) surrounded by ligands (NH3).
- **Ferrous Ammonium Sulfate** is a double salt, which is a combination of two salts that crystallize together but do not form a coordination complex.

### Step 3: Identify the odd one out
From the classification:
- Options 1, 2, and 4 are coordination compounds.
- Option 3 (Ferrous Ammonium Sulfate) is a double salt.

### Conclusion
Thus, the odd one out is **Ferrous Ammonium Sulfate** (Option 3).

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