Which compound on heating produces coloured metal oxide finally?

Options

A. `Al_(2)(SO_(4))_(3)`
B. `HgCO_(3)3Hg(OH)_(2)`
C. `Cu(NO_(3))_(2)`
D. `Ba(OH)_(2)`

Explanation

To solve the question of which compound, upon heating, produces a colored metal oxide, we will analyze each of the given options step by step.

### Step 1: Analyze the given compounds

We have the following compounds to consider:
1. Al₂(SO₄)₃ (Aluminum sulfate)
2. HgCO₃ (Mercury(II) carbonate)
3. Cu(NO₃)₂ (Copper(II) nitrate)
4. Ba(OH)₂ (Barium hydroxide)

### Step 2: Write the thermal decomposition reactions

**Option A: Al₂(SO₄)₃**
- On heating, it decomposes to form:
\[ \text{Al}_2(SO_4)_3 \rightarrow \text{Al}_2O_3 + 3SO_2 + \frac{3}{2}O_2 \]
- Aluminum oxide (Al₂O₃) is colorless.

**Option B: HgCO₃**
- On heating, it decomposes to form:
\[ \text{HgCO}_3 \rightarrow \text{Hg} + \text{CO}_2 \]
- This does not produce a metal oxide.

**Option C: Cu(NO₃)₂**
- On heating, it decomposes to form:
\[ \text{Cu(NO}_3)_2 \rightarrow \text{CuO} + 2NO_2 + \frac{1}{2}O_2 \]
- Copper oxide (CuO) is a colored metal oxide, typically black or brown.

**Option D: Ba(OH)₂**
- On heating, it decomposes to form:
\[ \text{Ba(OH)}_2 \rightarrow \text{BaO} + H_2O \]
- Barium oxide (BaO) is colorless.

### Step 3: Identify the colored metal oxide

From the reactions analyzed:
- **Al₂O₃** is colorless.
- **Hg** does not produce a metal oxide.
- **CuO** is colored (black/brown).
- **BaO** is colorless.

### Conclusion

The compound that produces a colored metal oxide upon heating is **Cu(NO₃)₂**, which forms **CuO**.

### Final Answer
**The answer is Cu(NO₃)₂ (Copper(II) nitrate).**

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