Of the four oxyacids of chlorine the strongest oxidising agent in dilute aqueous solution is :

Explanation

To determine which of the four oxyacids of chlorine is the strongest oxidizing agent in dilute aqueous solution, we will analyze the oxidation states of chlorine in each of the oxyacids. The four oxyacids of chlorine are:

1. Hypochlorous acid (HClO)
2. Chlorous acid (HClO2)
3. Chloric acid (HClO3)
4. Perchloric acid (HClO4)

### Step-by-Step Solution:

**Step 1: Determine the oxidation state of chlorine in each oxyacid.**

1. **For HClO:**
- The oxidation state of hydrogen (H) is +1.
- The oxidation state of oxygen (O) is -2.
- Let the oxidation state of chlorine (Cl) be \( x \).
- The equation becomes:
\[ +1 + x - 2 = 0 \implies x = +1 \]

2. **For HClO2:**
- The oxidation state of hydrogen (H) is +1.
- The oxidation state of oxygen (O) is -2 (there are 2 oxygens).
- Let the oxidation state of chlorine (Cl) be \( x \).
- The equation becomes:
\[ +1 + x - 2 \times 2 = 0 \implies +1 + x - 4 = 0 \implies x = +3 \]

3. **For HClO3:**
- The oxidation state of hydrogen (H) is +1.
- The oxidation state of oxygen (O) is -2 (there are 3 oxygens).
- Let the oxidation state of chlorine (Cl) be \( x \).
- The equation becomes:
\[ +1 + x - 3 \times 2 = 0 \implies +1 + x - 6 = 0 \implies x = +5 \]

4. **For HClO4:**
- The oxidation state of hydrogen (H) is +1.
- The oxidation state of oxygen (O) is -2 (there are 4 oxygens).
- Let the oxidation state of chlorine (Cl) be \( x \).
- The equation becomes:
\[ +1 + x - 4 \times 2 = 0 \implies +1 + x - 8 = 0 \implies x = +7 \]

**Step 2: Compare the oxidation states.**
- HClO: +1
- HClO2: +3
- HClO3: +5
- HClO4: +7

**Step 3: Identify the strongest oxidizing agent.**
The strength of an oxidizing agent increases with an increase in the oxidation state of the element that is being reduced. Since HClO4 has the highest oxidation state of +7, it is the strongest oxidizing agent among the four oxyacids.

### Conclusion:
The strongest oxidizing agent in dilute aqueous solution among the four oxyacids of chlorine is **HClO4 (Perchloric acid)**.

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