Which of the following is not a peroxy acid?

Options

A. Perphosphoric acid
B. Pernitric acid
C. Perdisulphuric acid
D. Perchloric acid

Explanation

To determine which of the following is not a peroxy acid, we need to understand what a peroxy acid is. A peroxy acid contains a peroxy linkage (–O–O–H) in its structure. Let's analyze each option step by step:

### Step 1: Identify the first option - Perphosphoric acid (H₃PO₅)
- **Structure**: Perphosphoric acid has the formula H₃PO₅. Its structure includes:
- One phosphorus atom (P) bonded to one double-bonded oxygen (O).
- Two hydroxyl groups (–OH).
- One peroxy linkage (–O–O–H).
- **Conclusion**: Since it contains a peroxy linkage, perphosphoric acid is a peroxy acid.

### Step 2: Identify the second option - Pernitric acid (HNO₄)
- **Structure**: Pernitric acid has the formula HNO₄. Its structure includes:
- One nitrogen atom (N) bonded to one double-bonded oxygen (O).
- One peroxy linkage (–O–O–H).
- **Conclusion**: Since it contains a peroxy linkage, pernitric acid is also a peroxy acid.

### Step 3: Identify the third option - Perdisulfuric acid (H₂S₂O₈)
- **Structure**: Perdisulfuric acid has the formula H₂S₂O₈. Its structure includes:
- Two sulfur atoms (S) bonded to double-bonded oxygens (O).
- Hydroxyl groups (–OH).
- A peroxy linkage between the two sulfur atoms.
- **Conclusion**: Since it contains a peroxy linkage, perdisulfuric acid is a peroxy acid.

### Step 4: Identify the fourth option - Perchloric acid (HClO₄)
- **Structure**: Perchloric acid has the formula HClO₄. Its structure includes:
- One chlorine atom (Cl) bonded to four oxygen atoms (O), with one of them being a hydroxyl group (–OH).
- There is no peroxy linkage present in this structure.
- **Conclusion**: Since it does not contain a peroxy linkage, perchloric acid is not a peroxy acid.

### Final Answer:
The compound that is not a peroxy acid is **Perchloric acid (HClO₄)**.

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