One mole of potassium dichromate completely oxidises the following number of moles of ferrous sulphate in acidic medium

Options

A. 1
B. 3
C. 5
D. 6

Explanation

To solve the problem of how many moles of ferrous sulfate are oxidized by one mole of potassium dichromate in acidic medium, we can follow these steps:

### Step 1: Write the balanced chemical equation
The reaction between potassium dichromate (K₂Cr₂O₇) and ferrous sulfate (FeSO₄) in acidic medium can be represented as follows:

\[ K_2Cr_2O_7 + FeSO_4 \rightarrow Cr^{3+} + Fe^{3+} + K^+ + SO_4^{2-} + H_2O \]

### Step 2: Identify oxidation states
In this reaction:
- Chromium in K₂Cr₂O₇ is reduced from +6 in Cr₂O₇²⁻ to +3 in Cr³⁺.
- Iron in FeSO₄ is oxidized from +2 in Fe²⁺ to +3 in Fe³⁺.

### Step 3: Determine the change in oxidation states
- The change for chromium:
\[ +6 \text{ (in K}_2Cr_2O_7\text{)} \rightarrow +3 \text{ (in Cr}^{3+}\text{)} \]
This means each chromium atom undergoes a reduction of 3 units.

- The change for iron:
\[ +2 \text{ (in FeSO}_4\text{)} \rightarrow +3 \text{ (in Fe}^{3+}\text{)} \]
This means each iron atom undergoes an oxidation of 1 unit.

### Step 4: Calculate the stoichiometry
Since there are 2 chromium atoms in one mole of potassium dichromate, the total change in oxidation state for chromium is:
\[ 2 \times 3 = 6 \]

For every 1 mole of K₂Cr₂O₇, it can oxidize 6 moles of Fe²⁺ (ferrous ions) to Fe³⁺ (ferric ions).

### Step 5: Conclusion
Thus, one mole of potassium dichromate completely oxidizes 6 moles of ferrous sulfate in acidic medium.

### Final Answer
**One mole of potassium dichromate oxidizes 6 moles of ferrous sulfate.**

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