Which of the following oxo acid(s) of sulphur have S - S bond ?

Options

A. Marshall acid
B. Pyrosulphuric acid
C. Pyrosulphurous acid
D. Dithionous acid

Answer

To determine which oxo acids of sulfur contain S-S bonds, we will analyze the given options step by step.

### Step 1: Identify the oxo acids of sulfur
We have four oxo acids of sulfur to consider:
1. Marshall acid (Peroxydisulfuric acid)
2. Pyrosulphuric acid
3. Pyrosulphurous acid
4. Dithenous acid

### Step 2: Analyze Marshall acid (Peroxydisulfuric acid)
- **Molecular Formula**: H2S2O8
- **Structure**: The structure consists of two sulfur atoms connected by oxygen atoms, with hydroxyl groups attached.
- **Conclusion**: There is no direct S-S bond present in Marshall acid.

### Step 3: Analyze Pyrosulphuric acid
- **Molecular Formula**: H2S2O7
- **Structure**: Similar to Marshall acid, the structure has sulfur atoms connected by oxygen atoms.
- **Conclusion**: There is no direct S-S bond present in Pyrosulphuric acid.

### Step 4: Analyze Pyrosulphurous acid
- **Molecular Formula**: H2S2O5
- **Structure**: The structure includes two sulfur atoms, and one of the sulfur atoms is double-bonded to an oxygen atom, while the other sulfur is connected to hydroxyl groups.
- **Conclusion**: There is a direct S-S bond present in Pyrosulphurous acid.

### Step 5: Analyze Dithenous acid
- **Molecular Formula**: H2S2O4
- **Structure**: The structure shows two sulfur atoms, with one sulfur atom double-bonded to oxygen and the other sulfur atom connected to hydroxyl groups.
- **Conclusion**: There is a direct S-S bond present in Dithenous acid.

### Final Answer
The oxo acids of sulfur that have S-S bonds are:
- Pyrosulphurous acid (Option 3)
- Dithenous acid (Option 4)

Thus, the correct options are 3 and 4.

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