The oxyacid of sulphur that contains a lone pair of electrons in sulphur is

Options

A. 1. sulphurous acid
B. 2. sulphuric acid
C. 3. peroxodisulphuric acid
D. 4. pyrosulphuric acid.

Explanation

To solve the question regarding which oxyacid of sulfur contains a lone pair of electrons on sulfur, we can analyze the given oxyacids step by step.

### Step 1: Identify the oxyacids of sulfur
The question asks for the oxyacid of sulfur that contains a lone pair of electrons on the sulfur atom. The common oxyacids of sulfur include:
1. Sulfurous acid (H₂SO₃)
2. Sulfuric acid (H₂SO₄)
3. Peroxodisulfuric acid (H₂S₂O₈)
4. Pyrosulfuric acid (H₂S₂O₇)

### Step 2: Analyze the structure of sulfurous acid (H₂SO₃)
- The chemical formula for sulfurous acid is H₂SO₃.
- The structure can be represented as follows:
- Sulfur (S) is bonded to three oxygen atoms (O) and has one lone pair of electrons.
- Therefore, sulfurous acid has a lone pair of electrons on the sulfur atom.

### Step 3: Analyze the structure of sulfuric acid (H₂SO₄)
- The chemical formula for sulfuric acid is H₂SO₄.
- The structure can be represented as follows:
- Sulfur (S) is bonded to four oxygen atoms (O) and does not have any lone pairs of electrons.
- Thus, sulfuric acid does not have a lone pair on the sulfur atom.

### Step 4: Analyze the structure of peroxodisulfuric acid (H₂S₂O₈)
- The chemical formula for peroxodisulfuric acid is H₂S₂O₈.
- The structure involves two sulfur atoms bonded to multiple oxygen atoms, and both sulfur atoms are fully bonded (covalency of 6 for each sulfur).
- Therefore, there are no lone pairs on the sulfur atoms in peroxodisulfuric acid.

### Step 5: Analyze the structure of pyrosulfuric acid (H₂S₂O₇)
- The chemical formula for pyrosulfuric acid is H₂S₂O₇.
- Similar to peroxodisulfuric acid, the structure consists of two sulfur atoms bonded to several oxygen atoms, with no lone pairs on the sulfur atoms.
- Thus, pyrosulfuric acid also does not have a lone pair on the sulfur atom.

### Conclusion
From the analysis, we can conclude that the only oxyacid of sulfur that contains a lone pair of electrons on sulfur is **sulfurous acid (H₂SO₃)**.

### Final Answer
The oxyacid of sulfur that contains a lone pair of electrons in sulfur is **sulfurous acid (H₂SO₃)**.

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