A compound `(A)` on heating in Busen flame imparts brick red colouration. `(A)` on heating gives `CO_(2)` gas and a residue `(B)`. The residue `(B)` when treated with water gives `(c )`. On passing an excess of `CO_(2)` through `(C )` in water, a clear solution `(D)` is obtained. On boiling `(D)`, compound `(A)` is reformed.
Compound `(A)` is

Options

A. `CaCO_(3)`
B. `MgCO_(3)`
C. `SrCO_(3)`
D. `BaCO_(3)`

Explanation

To solve the problem step by step, we need to analyze the given information about the compounds and their reactions.

### Step 1: Identify Compound A
The problem states that compound (A) imparts a brick red color when heated in a Bunsen flame. This coloration is characteristic of calcium compounds, particularly calcium carbonate (CaCO₃).

**Hint:** Look for color changes in flame tests associated with specific metal ions.

### Step 2: Heating Compound A
When compound (A) is heated, it produces carbon dioxide (CO₂) gas and a residue (B). The reaction for calcium carbonate when heated is:
\[ \text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g) \]
Here, the residue (B) is calcium oxide (CaO).

**Hint:** Consider the thermal decomposition reactions of common carbonates.

### Step 3: Treating Residue B with Water
The residue (B), which is CaO, reacts with water to form compound (C):
\[ \text{CaO} (s) + \text{H}_2\text{O} (l) \rightarrow \text{Ca(OH)}_2 (aq) \]
Compound (C) is calcium hydroxide (Ca(OH)₂).

**Hint:** Think about how metal oxides react with water to form hydroxides.

### Step 4: Passing CO₂ through Compound C
When excess CO₂ is passed through the solution of compound (C) in water, it forms a clear solution (D):
\[ \text{Ca(OH)}_2 (aq) + \text{CO}_2 (g) \rightarrow \text{Ca(HCO}_3)_2 (aq) \]
Compound (D) is calcium bicarbonate (Ca(HCO₃)₂).

**Hint:** Consider the reaction of hydroxides with acids or carbon dioxide to form bicarbonates.

### Step 5: Boiling Solution D
When solution (D) is boiled, it regenerates compound (A):
\[ \text{Ca(HCO}_3)_2 (aq) \rightarrow \text{CaCO}_3 (s) + \text{CO}_2 (g) + \text{H}_2\text{O} (l) \]
Thus, boiling leads to the formation of calcium carbonate (CaCO₃) again.

**Hint:** Think about how heating can drive off gases and reform solids.

### Conclusion
Based on the above steps and reactions, we conclude that compound (A) is calcium carbonate (CaCO₃).

**Final Answer:** Compound (A) is calcium carbonate (CaCO₃).

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