In thiosulphuric acid:

Options

A. each sulphur atom is in identical oxidation state
B. there is a S=S linkage present
C. one S atom is in +2 and other sulphur atom is in +4 oxidation state
D. there is only one replaceable hydrogen atom

Answer

To solve the question regarding thiosulphuric acid (H2S2O3), we will analyze the provided statements one by one, based on the structure and oxidation states of sulfur in the compound.

### Step-by-Step Solution:

1. **Identify the Chemical Structure**:
- Thiosulphuric acid is represented as H2S2O3. It contains two sulfur (S) atoms, three oxygen (O) atoms, and two hydrogen (H) atoms.
- The structural formula can be depicted as:
```
HO-S-S(=O)-OH
```
- Here, one sulfur atom is bonded to another sulfur atom (S-S bond), and the second sulfur atom is bonded to two hydroxyl (OH) groups and one oxygen atom.

2. **Determine the Oxidation States of Sulfur**:
- In thiosulphuric acid, we have two sulfur atoms.
- The first sulfur atom (the one in the S-S bond) has an oxidation state of 0 because it is bonded to another sulfur atom.
- The second sulfur atom, which is bonded to oxygen, has an oxidation state of +4. This is because it is bonded to two hydroxyl groups (each contributing -1) and one double-bonded oxygen (contributing -2), leading to a total oxidation state of +4.

3. **Evaluate Each Statement**:
- **Statement 1**: "Each sulfur atom is in identical oxidation state."
- This statement is **incorrect** because the oxidation states are 0 and +4 for the two sulfur atoms.

- **Statement 2**: "There is an S-S link present."
- This statement is **correct** as there is indeed a S-S bond in the structure of thiosulphuric acid.

- **Statement 3**: "One S atom is in +2 and the other in +4 oxidation state."
- This statement is **incorrect** because we determined the oxidation states to be 0 and +4, not +2.

- **Statement 4**: "There is only one replaceable hydrogen atom."
- This statement is **incorrect** because there are two replaceable hydrogen atoms (one from each OH group).

4. **Conclusion**:
- After evaluating all statements, only **Statement 2** is correct.

### Final Answer:
Only **Statement 2** is correct: "There is an S-S link present."