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

Options

A. `FeSO_(4)*(NH_(4))_(2)SO_(4)*6H_(2)O`
B. `K_(4)[Fe(CN)_(6)]`
C. `Fe_(2)O`
D. `Fe_(2)O_(3)`

Answer

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

### Step 1: Analyze Fe2O3
1. Let the oxidation state of iron (Fe) be \( X \).
2. In Fe2O3, there are 2 iron atoms and 3 oxygen atoms.
3. The oxidation state of oxygen is -2.
4. The overall charge of the compound is 0.
5. The equation can be set up as:
\[ 2X + 3(-2) = 0 \]
\[ 2X - 6 = 0 \]
\[ 2X = 6 \implies X = +3 \]
Therefore, the oxidation state of iron in Fe2O3 is +3.

### Step 2: Analyze Fe2O
1. Let the oxidation state of iron (Fe) be \( X \).
2. In Fe2O, there are 2 iron atoms and 1 oxygen atom.
3. The oxidation state of oxygen is -2.
4. The overall charge of the compound is 0.
5. The equation can be set up as:
\[ 2X + (-2) = 0 \]
\[ 2X - 2 = 0 \]
\[ 2X = 2 \implies X = +1 \]
Therefore, the oxidation state of iron in Fe2O is +1.

### Step 3: Analyze K4[Fe(CN)6]
1. Let the oxidation state of iron (Fe) be \( X \).
2. In K4[Fe(CN)6], there are 6 cyanide (CN) ligands, each with a charge of -1.
3. The overall charge of the complex ion is -4 (from K4, which has a +4 charge).
4. The equation can be set up as:
\[ X + 6(-1) = -4 \]
\[ X - 6 = -4 \]
\[ X = +2 \]
Therefore, the oxidation state of iron in K4[Fe(CN)6] is +2.

### Step 4: Analyze FeSO4
1. Let the oxidation state of iron (Fe) be \( X \).
2. In FeSO4, there is 1 sulfate (SO4) group, which has a charge of -2.
3. The overall charge of the compound is 0.
4. The equation can be set up as:
\[ X + (-2) = 0 \]
\[ X - 2 = 0 \]
\[ X = +2 \]
Therefore, the oxidation state of iron in FeSO4 is +2.

### Conclusion
Now we summarize the oxidation states calculated:
- Fe2O3: +3
- Fe2O: +1
- K4[Fe(CN)6]: +2
- FeSO4: +2

The compound in which iron has the lowest oxidation number is **Fe2O**, where the oxidation state of iron is **+1**.

### Final Answer
The compound in which iron has the lowest oxidation number is **Fe2O**.

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