(i) A white solid mixture of two salts containing a common cations in insoluble in water. It dissolves in dilute HCl producing some gases (with effervescence) that turn an acidified dichromate solution gren. After the gases are passed through the acidified dichromate solution, the emerging gas turns baryta water milky.
(ii) On treatment with dilute `HNO_(3)`, the white solid gives a solution which does not directly give a precipitate with a `BaCl_(2)` solution but gives a white precipitate when warmed with `H_(2)O_(2)` and then treated with a `BaCl_(2)` solution.
(iii) The solution of the mixture in dilute HCl, when treated with `NH_(4)Cl,NH_(4)OH and ` an `Na_(2)HPO_(4)` solution, gives a white precipitate.
Q. The gases evolved in (i) are:

Options

A. `CO_(2) and HCl`
B. `SO_(2) and CO_(2)`
C. `SO_(2) and H_(2)S`
D. `NH_(3) and CO_(2)`

Answer

To solve the problem step-by-step, we will analyze the information provided in the question and deduce the gases evolved based on the reactions described.

### Step 1: Identify the salts in the mixture
The question states that the white solid mixture contains two salts with a common cation that is insoluble in water. The presence of a common cation suggests that the salts could be carbonates and sulfites, as these anions are known to produce gases when reacted with acids.

**Hint**: Look for anions that produce gases when reacting with dilute acids.

### Step 2: Reaction with dilute HCl
When the white solid mixture is treated with dilute HCl, it produces gases with effervescence. The two possible reactions are:
1. Carbonate ion (CO₃²⁻) reacts with HCl to produce carbon dioxide (CO₂):
\[ \text{CO}_3^{2-} + 2\text{H}^+ \rightarrow \text{CO}_2 + \text{H}_2\text{O} \]
2. Sulfite ion (SO₃²⁻) reacts with HCl to produce sulfur dioxide (SO₂):
\[ \text{SO}_3^{2-} + 2\text{H}^+ \rightarrow \text{SO}_2 + \text{H}_2\text{O} \]

**Hint**: Identify the products of the reactions with dilute HCl.

### Step 3: Analyze the gases produced
The gases produced from the reactions above are:
- Carbon dioxide (CO₂)
- Sulfur dioxide (SO₂)

The question mentions that the gases turn an acidified dichromate solution green, which is a characteristic reaction of sulfur dioxide (SO₂). Additionally, when CO₂ is passed through lime water, it turns milky, confirming the presence of CO₂.

**Hint**: Consider the color change in dichromate solution and the reaction with lime water to confirm the gases.

### Step 4: Conclusion
Based on the reactions and the observations, the gases evolved when the white solid mixture is treated with dilute HCl are:
- Carbon dioxide (CO₂)
- Sulfur dioxide (SO₂)

Thus, the answer to the question is that the gases evolved are CO₂ and SO₂.

**Final Answer**: The gases evolved in (i) are CO₂ and SO₂.