Which one is most stable to heat ?

Options

A. HClO
B. `HClO_2`
C. `HClO_3`
D. `HClO_4`

Answer

To determine which of the given oxoacids is most stable to heat, we need to analyze the oxidation states of chlorine in each compound and how that affects stability.

### Step-by-Step Solution:

1. **Identify the Compounds**: The given compounds are HClO (hypochlorous acid), HClO2 (chlorous acid), HClO3 (chloric acid), and HClO4 (perchloric acid).

2. **Determine the Oxidation States of Chlorine**:
- For HClO:
- Let the oxidation state of chlorine be \( x \).
- The equation is: \( +1 + x - 2 = 0 \) (from H and O)
- Solving gives \( x = +1 \).
- For HClO2:
- Let the oxidation state of chlorine be \( y \).
- The equation is: \( +1 + y - 4 = 0 \)
- Solving gives \( y = +3 \).
- For HClO3:
- Let the oxidation state of chlorine be \( z \).
- The equation is: \( +1 + z - 6 = 0 \)
- Solving gives \( z = +5 \).
- For HClO4:
- Let the oxidation state of chlorine be \( p \).
- The equation is: \( +1 + p - 8 = 0 \)
- Solving gives \( p = +7 \).

3. **Analyze the Stability**:
- The stability of oxoacids generally increases with the oxidation state of the central atom (in this case, chlorine).
- Higher oxidation states lead to smaller cation sizes, which increases covalent character in the bond, making the compound more stable to heat.

4. **Rank the Oxoacids Based on Oxidation States**:
- HClO: +1
- HClO2: +3
- HClO3: +5
- HClO4: +7

5. **Conclusion**:
- Since HClO4 has the highest oxidation state of +7, it is the most stable to heat among the given oxoacids.

### Final Answer:
**HClO4 is the most stable to heat.**