Sodium sulphite `(Na_(2)SO_(3))` is added to meat as a preservative. The presence of `Na_(2)SO_(4)` can be detected by adding dil. `H_(2)SO_(4)` when the pungent smelling gas evolved turns the lime water milky. The gas evolved was detected as sulphur dioxide. The `SO_(2) " to "SO_(4)^(2-)` in titration.
`SO_(2)+2H_(2)O+I_(2) to 4H^(+)+SO_(4)^(2-)+2I^(-)`
In order to check the results of titration, excess barium chloride is added to the final solution. The resulting precipitate is collected and weighed.
Q. `SO_(2) and CO_(2)` both lime water milky. Which of the following reagent can be used to distinguish these two gases?
(I)`K_(2)Cr_(2)O_(7)"/"H_(2)SO_(4)` (II)`KMnO_(4)"/"H^(+)` (III)`I_(2)` solution

Options

A. II, II, III correct
B. I. III only correct
C. II, III only correct
D. III only correct

Answer

To distinguish between sulfur dioxide (SO₂) and carbon dioxide (CO₂), we can use specific reagents that react differently with these gases. Here’s a step-by-step solution to the problem:

### Step 1: Understanding the Gases
- **Sulfur Dioxide (SO₂)**: A pungent gas that can reduce other substances and can be oxidized to sulfate ions (SO₄²⁻).
- **Carbon Dioxide (CO₂)**: A colorless gas that does not have reducing properties and is already in its highest oxidation state (+4).

### Step 2: Identifying the Reagents
We have three reagents to consider:
1. Potassium dichromate (K₂Cr₂O₇) in the presence of sulfuric acid (H₂SO₄)
2. Potassium permanganate (KMnO₄) in the presence of H⁺ ions
3. Iodine solution (I₂)

### Step 3: Analyzing the Reactions
- **Potassium Dichromate (K₂Cr₂O₇)**:
- SO₂ can reduce Cr₂O₇²⁻ (orange) to Cr³⁺ (green), indicating the presence of SO₂.
- CO₂ does not react and does not change the color.

- **Potassium Permanganate (KMnO₄)**:
- SO₂ can reduce MnO₄⁻ (purple) to Mn²⁺ (colorless), indicating the presence of SO₂.
- CO₂ does not reduce KMnO₄ and will not change its color.

- **Iodine Solution (I₂)**:
- SO₂ can reduce I₂ to I⁻, causing a color change (from brown to colorless).
- CO₂ does not react with iodine.

### Step 4: Conclusion
All three reagents (I, II, and III) can be used to distinguish between SO₂ and CO₂ because only SO₂ can reduce these reagents, while CO₂ cannot.

Thus, the answer is that all three reagents can be used to distinguish between sulfur dioxide and carbon dioxide.

### Final Answer
The reagents that can be used to distinguish between SO₂ and CO₂ are:
- (I) K₂Cr₂O₇/H₂SO₄
- (II) KMnO₄/H⁺
- (III) I₂ solution