Pernitric acid is

Options

A. `HNO_2`
B. `HNO_3`
C. `HNO_4`
D. `HNO`

Answer

To determine what pernitric acid is, we will analyze the given options and identify the correct chemical formula for pernitric acid.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- (a) HNO2
- (b) HNO3
- (c) HNO4
- (d) HNO

2. **Analyze Each Option**:
- **Option (a) HNO2**: This is known as nitrous acid, which is not pernitric acid.
- **Option (b) HNO3**: This is nitric acid, a strong acid and a powerful oxidizing agent, but it is not pernitric acid.
- **Option (c) HNO4**: This is identified as pernitric acid.
- **Option (d) HNO**: This is called nitroxyl, which is a weak acid and not related to pernitric acid.

3. **Conclusion**: Based on the analysis, the correct answer is:
- **Pernitric acid is HNO4**.

4. **Preparation of Pernitric Acid**:
- Pernitric acid (HNO4) can be prepared by reacting nitric acid (HNO3) with hydrogen peroxide (H2O2):
\[ HNO3 + H2O2 \rightarrow HNO4 + H2O \]

### Final Answer:
Pernitric acid is **HNO4**.

---