In which of the following compounds iron has lowest oxidation state?

Options

A. `FeSO_(4).(NH_(4))_(2)SO_(4).6H_(2)O`
B. `K_(4)Fe(CN)_(6)`
C. `Fe(CO)_(5)`
D. `Fe_(2)O`

Explanation

To determine the oxidation state of iron in the given compounds and identify which one has the lowest oxidation state, we will analyze each compound step by step.

### Step 1: Calculate the oxidation state of iron in FeSO4·(NH4)2SO4·6H2O

1. **Identify the components**:
- Iron (Fe) = X (unknown oxidation state)
- Sulfate (SO4) = -2
- Ammonium (NH4) = +1
- Water (H2O) = 0 (does not contribute to charge)

2. **Set up the equation**:
The total charge must equal zero:
\[ X + (-2) + 2(+1) + (-2) + 6(0) = 0 \]
Simplifying this gives:
\[ X - 2 + 2 - 2 = 0 \implies X = +2 \]

### Step 2: Calculate the oxidation state of iron in K4[Fe(CN)6]

1. **Identify the components**:
- Potassium (K) = +1
- Cyanide (CN) = -1
- Iron (Fe) = X

2. **Set up the equation**:
The total charge must equal zero:
\[ 4(+1) + X + 6(-1) = 0 \]
Simplifying this gives:
\[ 4 + X - 6 = 0 \implies X = +2 \]

### Step 3: Calculate the oxidation state of iron in Fe(CO)5

1. **Identify the components**:
- Carbon monoxide (CO) = 0 (neutral molecule)
- Iron (Fe) = X

2. **Set up the equation**:
The total charge must equal zero:
\[ X + 5(0) = 0 \]
Thus:
\[ X = 0 \]

### Step 4: Calculate the oxidation state of iron in Fe2O3

1. **Identify the components**:
- Oxygen (O) = -2
- Iron (Fe) = X

2. **Set up the equation**:
The total charge must equal zero:
\[ 2X + 3(-2) = 0 \]
Simplifying this gives:
\[ 2X - 6 = 0 \implies 2X = 6 \implies X = +3 \]

### Summary of oxidation states:
- FeSO4·(NH4)2SO4·6H2O: +2
- K4[Fe(CN)6]: +2
- Fe(CO)5: 0
- Fe2O3: +3

### Conclusion:
The compound in which iron has the lowest oxidation state is **Fe(CO)5**, where the oxidation state of iron is 0.

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