Which of the following is not a peroxy acid?

Options

A. Perphosphoric Acid
B. Pernitric Acid
C. Perdisulphuric Acid
D. perchloric acid

Answer

To determine which of the following is not a peroxy acid, we need to analyze each option provided:

1. **Understanding Peroxy Acids**:
- A peroxy acid is defined as an acid that contains a peroxo group, which is characterized by the presence of an O-O (peroxo) linkage. This means that in the structure of a peroxy acid, there will be a -OOH (hydroperoxy) group.

2. **Analyzing the Options**:
- **Option A: Perphosphoric Acid (H₃PO₅)**:
- This acid contains a peroxo group in its structure. Therefore, it is a peroxy acid.
- **Option B: Pernitric Acid (HNO₄)**:
- This acid also contains a peroxo group, making it a peroxy acid.
- **Option C: Perdisulfuric Acid (H₂S₂O₈)**:
- This acid contains a peroxo linkage as well, qualifying it as a peroxy acid.
- **Option D: Perchloric Acid (HClO₄)**:
- This acid does not contain a peroxo group. Its structure is characterized by chlorine double-bonded to oxygen atoms, and it does not have an O-O linkage. Hence, it is not a peroxy acid.

3. **Conclusion**:
- Based on the analysis, the acid that is not a peroxy acid is **Perchloric Acid (HClO₄)**. Therefore, the correct answer is option D.

### Summary of the Steps:
1. Define what a peroxy acid is.
2. Examine each option to check for the presence of a peroxo group.
3. Identify that Perchloric Acid does not contain a peroxo group.
4. Conclude that Perchloric Acid is not a peroxy acid.