Which of the following is not a thermal decomposition reaction?

Options

A. `2H_(2)Oto2H_(2)+O_(2)`
B. `2FeSO_(4)toFe_(2)O_(3)+SO_(2)+SO_(3)`
C. `ZnCO_(3)toZnO+CO_(2)`
D. `2KClO_(3)to2KCl+3O_(2)`

Explanation

To determine which of the following is not a thermal decomposition reaction, we need to understand what a thermal decomposition reaction is. A thermal decomposition reaction occurs when a single reactant breaks down into two or more products due to the application of heat.

### Step-by-Step Solution:

1. **Identify the Definition of Thermal Decomposition:**
- A thermal decomposition reaction is a type of decomposition reaction where a compound breaks down into simpler substances when heated.

2. **Analyze Each Option:**
- **Option 1: Water (H2O) decomposing into H2 and O2.**
- This reaction does not occur through heating but rather through electrolysis, where an electric current is passed through water to decompose it. Therefore, this is not a thermal decomposition reaction.

- **Option 2: Iron(II) sulfate (FeSO4) decomposing into Fe2O3, SO2, and SO3.**
- This reaction occurs upon heating, making it a thermal decomposition reaction.

- **Option 3: Zinc carbonate (ZnCO3) decomposing into zinc oxide (ZnO) and carbon dioxide (CO2).**
- This reaction also occurs when heated, classifying it as a thermal decomposition reaction.

- **Option 4: Potassium chlorate (KClO3) decomposing into potassium chloride (KCl) and oxygen (O2).**
- This reaction is another example of thermal decomposition as it occurs when heated.

3. **Conclusion:**
- Based on the analysis, the reaction involving water (H2O) decomposing into hydrogen and oxygen is the only one that is not a thermal decomposition reaction. Instead, it is an electrolytic decomposition reaction.

### Final Answer:
The reaction that is not a thermal decomposition reaction is the decomposition of water (H2O) into hydrogen (H2) and oxygen (O2).

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