Which gas is evolved when `PbO_(2)` is treated with conc `HNO_(3)` ?

Options

A. `NO_(2)`
B. `O_(2)`
C. `N_(2)`
D. `N_(2)O`

Explanation

To determine which gas is evolved when PbO2 (lead(IV) oxide) is treated with concentrated HNO3 (nitric acid), we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are lead(IV) oxide (PbO2) and concentrated nitric acid (HNO3).

### Step 2: Understand the Nature of PbO2
Lead(IV) oxide (PbO2) is known to be a powerful oxidizing agent. This property is crucial as it indicates that PbO2 can facilitate the release of oxygen gas (O2) during the reaction.

### Step 3: Write the Balanced Chemical Equation
When PbO2 reacts with concentrated HNO3, the products formed are lead nitrate (Pb(NO3)2), water (H2O), and oxygen gas (O2). The balanced chemical equation can be represented as follows:

\[ 2 \, \text{PbO}_2 + 4 \, \text{HNO}_3 \rightarrow 2 \, \text{Pb(NO}_3\text{)}_2 + 2 \, \text{H}_2\text{O} + \text{O}_2 \]

### Step 4: Identify the Evolved Gas
From the balanced equation, we can see that oxygen gas (O2) is one of the products formed during the reaction.

### Conclusion
Therefore, when PbO2 is treated with concentrated HNO3, the gas that is evolved is **oxygen (O2)**.

### Final Answer
The gas evolved is **oxygen (O2)**.

---