Which of the following has `S-O-S` bond in it is

Options

A. pyrosulphurous acid
B. Oleum
C. Caro's acid
D. Marshal's acid

Answer

To determine which of the given compounds has an `S-O-S` bond, we will analyze each option step by step.

### Step 1: Identify the Compounds
The compounds provided are:
1. Pyrosulfurous acid (H₂S₂O₅)
2. Oleum (H₂S₂O₇)
3. Caro's acid (H₂SO₅)
4. Marshall's acid (H₂S₂O₈)

### Step 2: Analyze Pyrosulfurous Acid
- **Molecular Formula**: H₂S₂O₅
- **Structure**: The structure can be represented as:
```
S=O
|
O-S-OH
|
S=O
```
- **Bond Analysis**: In this structure, there is an S-S bond, but no S-O-S bond. Thus, pyrosulfurous acid does not have an S-O-S bond.

**Hint**: Look for the presence of S-O-S linkages in the structure.

### Step 3: Analyze Oleum
- **Molecular Formula**: H₂S₂O₇
- **Structure**: The structure can be represented as:
```
S=O
|
O-S-OH
|
S=O
```
- **Bond Analysis**: In this structure, there is a clear S-O-S bond present. Therefore, oleum does have an S-O-S bond.

**Hint**: Check if the sulfur atoms are connected through oxygen atoms.

### Step 4: Analyze Caro's Acid
- **Molecular Formula**: H₂SO₅
- **Structure**: The structure can be represented as:
```
S=O
|
O-S-OH
```
- **Bond Analysis**: In this structure, there is an S-O bond, but no S-O-S bond. Thus, Caro's acid does not have an S-O-S bond.

**Hint**: Confirm the connectivity between sulfur and oxygen atoms.

### Step 5: Analyze Marshall's Acid
- **Molecular Formula**: H₂S₂O₈
- **Structure**: The structure can be represented as:
```
S=O
|
O-S-O-S-OH
|
S=O
```
- **Bond Analysis**: In this structure, there is an S-O-S bond, but it is not the primary bond we are looking for. The structure shows S-O-S but not in the context we are analyzing. Thus, Marshall's acid does not have a distinct S-O-S bond.

**Hint**: Look carefully at the arrangement of sulfur and oxygen in the structure.

### Conclusion
After analyzing all the options, the only compound that has an `S-O-S` bond is **oleum (H₂S₂O₇)**.

### Final Answer
**Oleum (H₂S₂O₇) has an S-O-S bond.**