How many moles of acidified `FeSO_4` solution can be completely oxidised by one mole of `KMnO_4` ?

Options

A. 10
B. 5
C. 6
D. 2

Explanation

To determine how many moles of acidified `FeSO4` solution can be completely oxidized by one mole of `KMnO4`, we will follow these steps:

### Step 1: Write the balanced reaction of `KMnO4` in acidic medium
The first step is to write the balanced chemical equation for the reaction of potassium permanganate (`KMnO4`) in an acidic medium. The balanced equation is:

\[ 2 KMnO_4 + 3 H_2SO_4 \rightarrow K_2SO_4 + 3 MnSO_4 + 3 H_2O + 5 O \]

This shows that 2 moles of `KMnO4` react with 3 moles of sulfuric acid to produce 1 mole of potassium sulfate, 3 moles of manganese sulfate, and 5 moles of nascent oxygen.

### Step 2: Write the oxidation reaction of `FeSO4`
Next, we need to write the oxidation reaction of ferrous sulfate (`FeSO4`) with nascent oxygen. The reaction can be represented as:

\[ 2 FeSO_4 + O \rightarrow Fe_2(SO_4)_3 + H_2O \]

This indicates that 2 moles of ferrous sulfate react with 1 mole of nascent oxygen to produce 1 mole of ferric sulfate.

### Step 3: Relate the two reactions
From the balanced equation of `KMnO4`, we see that 2 moles of `KMnO4` produce 5 moles of nascent oxygen. Therefore, 1 mole of `KMnO4` will produce:

\[ \frac{5}{2} = 2.5 \text{ moles of nascent oxygen} \]

### Step 4: Determine how many moles of `FeSO4` can be oxidized
Since 2 moles of `FeSO4` require 1 mole of nascent oxygen, we can find out how many moles of `FeSO4` can be oxidized by 2.5 moles of nascent oxygen:

From the reaction:

\[ 2 \text{ moles of } FeSO_4 \text{ react with } 1 \text{ mole of } O \]

Thus, 2.5 moles of nascent oxygen can oxidize:

\[ 2 \times 2.5 = 5 \text{ moles of } FeSO_4 \]

### Final Answer
Therefore, 1 mole of `KMnO4` can completely oxidize **5 moles of acidified `FeSO4`** solution.

### Summary
The final answer is **5 moles** of `FeSO4`.

---