A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes maximum change in the oxidation number?

Options

A. `Cl`
B. `C`
C. `S`
D. `H`

Explanation

To determine which element undergoes the maximum change in oxidation number during the reaction of potassium chlorate, oxalic acid, and sulfuric acid when heated, we can follow these steps:

### Step 1: Write the balanced chemical equation
The reaction can be written as:
\[ \text{KClO}_3 + \text{H}_2\text{C}_2\text{O}_4 + \text{H}_2\text{SO}_4 \rightarrow \text{K}_2\text{SO}_4 + \text{KCl} + \text{CO}_2 + \text{H}_2\text{O} \]

### Step 2: Assign oxidation numbers to each element
- **Potassium (K)**: In both KClO3 and K2SO4, K has an oxidation state of +1.
- **Chlorine (Cl)**: In KClO3, Cl has an oxidation state of +5. In KCl, Cl has an oxidation state of -1.
- **Carbon (C)**: In H2C2O4, C has an oxidation state of +3. In CO2, C has an oxidation state of +4.
- **Sulfur (S)**: In H2SO4, S has an oxidation state of +6. In K2SO4, S remains +6.
- **Oxygen (O)**: In all compounds, O has an oxidation state of -2.

### Step 3: Calculate the change in oxidation numbers
- **Potassium (K)**: +1 to +1 → Change = 0
- **Chlorine (Cl)**: +5 to -1 → Change = 6
- **Carbon (C)**: +3 to +4 → Change = 1
- **Sulfur (S)**: +6 to +6 → Change = 0
- **Oxygen (O)**: Not considered as it remains -2.

### Step 4: Identify the maximum change
From the calculations:
- K: Change = 0
- Cl: Change = 6
- C: Change = 1
- S: Change = 0

The element that undergoes the maximum change in oxidation number is **Chlorine (Cl)**, which changes from +5 to -1, resulting in a total change of 6.

### Final Answer
The element that undergoes the maximum change in oxidation number during the reaction is **Chlorine (Cl)**.

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