In a reaction KCl is converted into `KClO_4`. Change in oxidation number is :

Explanation

To determine the change in oxidation number when KCl is converted into KClO₄, we can follow these steps:

### Step 1: Identify the oxidation states in KCl
- In KCl, potassium (K) is an alkali metal and has an oxidation state of +1.
- Let the oxidation state of chlorine (Cl) be \( x \).
- The compound is neutral, so the sum of oxidation states must equal 0:
\[ +1 + x = 0 \]
Solving for \( x \):
\[ x = -1 \]
- Therefore, the oxidation state of Cl in KCl is -1.

### Step 2: Identify the oxidation states in KClO₄
- In KClO₄, potassium (K) again has an oxidation state of +1.
- Let the oxidation state of chlorine (Cl) be \( y \).
- Oxygen (O) has an oxidation state of -2. Since there are 4 oxygen atoms, their total contribution is \( 4 \times (-2) = -8 \).
- The compound is neutral, so the sum of oxidation states must equal 0:
\[ +1 + y + (-8) = 0 \]
Solving for \( y \):
\[ y - 7 = 0 \implies y = +7 \]
- Therefore, the oxidation state of Cl in KClO₄ is +7.

### Step 3: Calculate the change in oxidation number
- The change in oxidation number can be calculated as:
\[ \text{Change} = \text{Final oxidation state} - \text{Initial oxidation state} \]
- Substituting the values we found:
\[ \text{Change} = +7 - (-1) = +7 + 1 = +8 \]

### Conclusion
The change in oxidation number when KCl is converted to KClO₄ is +8.

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