Which of the following compound does not liberated oxygen gas on warming with conc. `H_(2)SO_(4)` ?

Options

A. `SO_(3)`
B. `PbO_(2)`
C. `MnO_(2)`
D. `CrO_(5)`

Explanation

To determine which compound does not liberate oxygen gas when warmed with concentrated sulfuric acid (H₂SO₄), we will analyze the reactions of each compound with concentrated H₂SO₄.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to analyze:
- SO₃ (sulfur trioxide)
- PbO₂ (lead dioxide)
- MnO₂ (manganese dioxide)
- CrO₅ (chromium pentoxide)

2. **Reaction of SO₃ with Concentrated H₂SO₄**:
- When SO₃ is heated with concentrated H₂SO₄, it forms oleum (H₂S₂O₇).
- **Reaction**:
\[ \text{SO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{H}_2\text{S}_2\text{O}_7 \]
- **Oxygen Liberation**: No oxygen gas is liberated.

3. **Reaction of PbO₂ with Concentrated H₂SO₄**:
- When PbO₂ is heated with concentrated H₂SO₄, it produces lead(II) sulfate (PbSO₄), water (H₂O), and liberates oxygen gas.
- **Reaction**:
\[ \text{PbO}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{PbSO}_4 + \text{H}_2\text{O} + \frac{1}{2} \text{O}_2 \]
- **Oxygen Liberation**: Oxygen gas is liberated.

4. **Reaction of MnO₂ with Concentrated H₂SO₄**:
- When MnO₂ is heated with concentrated H₂SO₄, it produces manganese(II) sulfate (MnSO₄), water (H₂O), and liberates oxygen gas.
- **Reaction**:
\[ \text{MnO}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{MnSO}_4 + \text{H}_2\text{O} + \frac{1}{2} \text{O}_2 \]
- **Oxygen Liberation**: Oxygen gas is liberated.

5. **Reaction of CrO₅ with Concentrated H₂SO₄**:
- When CrO₅ is heated with concentrated H₂SO₄, it produces chromium(II) sulfate and liberates oxygen gas.
- **Reaction**:
\[ \text{CrO}_5 + \text{H}_2\text{SO}_4 \rightarrow \text{Cr}_2\text{SO}_4 + \text{O}_2 \]
- **Oxygen Liberation**: Oxygen gas is liberated.

6. **Conclusion**:
- From the analysis, it is clear that:
- SO₃ does not liberate oxygen gas.
- PbO₂, MnO₂, and CrO₅ all liberate oxygen gas.
- Therefore, the compound that does not liberate oxygen gas on warming with concentrated H₂SO₄ is **SO₃**.

### Final Answer:
**SO₃ (sulfur trioxide)** does not liberate oxygen gas on warming with concentrated H₂SO₄.

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