Which of the following does not give oxygen on heating?

Options

A. `KClO_3`
B. `K_2Cr_2O_7`
C. `KMnO_4`
D. None

Answer

To solve the question of which compound does not give oxygen on heating, we will analyze each of the given compounds: KClO3, K2Cr2O7, and KMnO4.

### Step-by-Step Solution:

1. **Analyze KClO3 (Potassium Chlorate)**:
- When KClO3 is heated, it decomposes to form potassium chloride (KCl) and oxygen gas (O2).
- The balanced equation for this reaction is:
\[ 2 \text{KClO}_3 \rightarrow 2 \text{KCl} + 3 \text{O}_2 \]
- Conclusion: KClO3 gives oxygen on heating.

2. **Analyze K2Cr2O7 (Potassium Dichromate)**:
- When K2Cr2O7 is heated, it decomposes to form potassium chromate (K2CrO4), chromium(III) oxide (Cr2O3), and oxygen gas (O2).
- The balanced equation for this reaction is:
\[ 4 \text{K}_2\text{Cr}_2\text{O}_7 \rightarrow 4 \text{K}_2\text{CrO}_4 + 2 \text{Cr}_2\text{O}_3 + 3 \text{O}_2 \]
- Conclusion: K2Cr2O7 gives oxygen on heating.

3. **Analyze KMnO4 (Potassium Permanganate)**:
- When KMnO4 is heated, it decomposes to form potassium manganate (K2MnO4), manganese dioxide (MnO2), and oxygen gas (O2).
- The balanced equation for this reaction is:
\[ 2 \text{KMnO}_4 \rightarrow \text{K}_2\text{MnO}_4 + \text{MnO}_2 + \text{O}_2 \]
- Conclusion: KMnO4 gives oxygen on heating.

4. **Evaluate the Options**:
- All three compounds (KClO3, K2Cr2O7, and KMnO4) produce oxygen when heated.
- The last option is "none of these," which implies that none of the above compounds fail to produce oxygen on heating.

### Final Answer:
- The correct answer is **D) None of these**.