In netural of faintly alkaline medium, thiosulphate is quantitatively oxidized by `KMnO_(4)` to

Options

A. `SO_3^(2-)`
B. `SO_4^(2-)`
C. `SO_2`
D. `SO_5^(2-)`

Explanation

To solve the problem of how thiosulfate is oxidized by potassium permanganate (KMnO₄) in a neutral or faintly alkaline medium, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this reaction are thiosulfate (H₂O₃S²⁻) and potassium permanganate (KMnO₄). In solution, KMnO₄ dissociates to give MnO₄⁻ ions.

2. **Determine the Medium**:
- The reaction occurs in a neutral or faintly alkaline medium. This means that the pH is around 7 or slightly above, which can influence the products formed during the oxidation.

3. **Write the Half-Reactions**:
- The oxidation half-reaction for thiosulfate can be represented as:
\[ H₂O₃S²⁻ \rightarrow SO₄²⁻ \]
- The reduction half-reaction for permanganate in neutral medium can be represented as:
\[ MnO₄⁻ + 8H⁺ + 5e⁻ \rightarrow Mn²⁺ + 4H₂O \]
- However, in a neutral medium, the MnO₄⁻ is reduced to MnO₂ instead of Mn²⁺.

4. **Combine the Half-Reactions**:
- To balance the overall reaction, we need to ensure that the electrons lost in the oxidation half-reaction equal the electrons gained in the reduction half-reaction. The balanced reaction can be written as:
\[ 3H₂O₃S²⁻ + 8MnO₄⁻ + 6H₂O \rightarrow 8MnO₂ + 6SO₄²⁻ + 2OH⁻ \]
- This shows that thiosulfate is oxidized to sulfate ions (SO₄²⁻).

5. **Identify the Products**:
- From the balanced equation, we see that the primary product of the oxidation of thiosulfate by KMnO₄ in a neutral medium is sulfate (SO₄²⁻).

6. **Select the Correct Option**:
- Among the given options:
1. SO₃²⁻ (not correct)
2. SO₄²⁻ (correct)
3. SO₂ (not correct)
4. SO₅²⁻ (not correct)
- Therefore, the correct answer is option 2: SO₄²⁻.

### Final Answer:
Thiosulfate is quantitatively oxidized by KMnO₄ to produce sulfate ions (SO₄²⁻).