The gas obtained by roasting of sulphide ore is reacted with acidified potassium dichromate. A green colored compound 'X' is formed. The compound X can be :

Options

A. `SO_(2)`
B. `Cr_(2)(SO_4)_(3)`
C. `Cl_(2)`
D. `CrO_(2)Cl_(2)`

Answer

To solve the question, we need to identify the gas produced by roasting a sulphide ore and its reaction with acidified potassium dichromate, which leads to the formation of a green-colored compound 'X'.

### Step 1: Identify the gas produced by roasting sulphide ore
- Roasting is a process where a sulphide ore is heated in the presence of oxygen.
- For example, if we take lead(II) sulphide (PbS) or zinc sulphide (ZnS), they react with oxygen to form their respective oxides and release sulfur dioxide (SO2) gas.

**Hint:** Remember that roasting involves heating sulphide ores in the presence of oxygen, leading to the formation of oxides and the release of SO2 gas.

### Step 2: Reaction of SO2 with acidified potassium dichromate
- The next step is to consider the reaction of sulfur dioxide (SO2) with acidified potassium dichromate (K2Cr2O7).
- Acidified potassium dichromate is a strong oxidizing agent. In acidic conditions, SO2 can be oxidized to sulfuric acid (H2SO4).

**Hint:** Acidified potassium dichromate is used as an oxidizing agent; think about how it reacts with reducing agents like SO2.

### Step 3: Formation of the green-colored compound
- The reaction can be summarized as follows:
\[ SO_2 + K_2Cr_2O_7 + H_2SO_4 \rightarrow K_2SO_4 + Cr_2(SO_4)_3 + H_2O \]
- The chromium in potassium dichromate (Cr^6+) is reduced to Cr^3+, which is responsible for the green color of the compound formed, specifically chromium(III) sulfate (Cr2(SO4)3).

**Hint:** The color change from orange (due to Cr^6+) to green (due to Cr^3+) is a key indicator of the reaction taking place.

### Conclusion
- The green-colored compound 'X' formed in this reaction is chromium(III) sulfate (Cr2(SO4)3).

**Final Answer:** The compound X can be chromium(III) sulfate (Cr2(SO4)3).

### Summary of Steps:
1. Identify the gas produced by roasting sulphide ore (SO2).
2. Understand the reaction of SO2 with acidified potassium dichromate.
3. Recognize the formation of the green-colored compound (Cr2(SO4)3).