The metal oxide which decomposes on heating, is:

Options

A. ZnO
B. `Al_(2)O_(3)`
C. `Ag_(2)O`
D. `HgO`

Answer

To determine which metal oxide decomposes upon heating, we will analyze the given options: zinc oxide (ZnO), aluminum oxide (Al2O3), silver oxide (Ag2O), and mercury(II) oxide (HgO).

### Step-by-Step Solution:

1. **Identify the Metal Oxides**:
We have four metal oxides to consider:
- Zinc oxide (ZnO)
- Aluminum oxide (Al2O3)
- Silver oxide (Ag2O)
- Mercury(II) oxide (HgO)

2. **Analyze Each Oxide for Decomposition**:
- **Zinc Oxide (ZnO)**:
- Zinc oxide is stable and does not decompose upon heating under normal conditions.
- **Aluminum Oxide (Al2O3)**:
- Aluminum oxide is also very stable and does not decompose upon heating.
- **Silver Oxide (Ag2O)**:
- Silver oxide is known to decompose upon heating to yield silver (Ag) and oxygen gas (O2). The reaction is:
\[ 2Ag2O \rightarrow 4Ag + O2 \]
- **Mercury(II) Oxide (HgO)**:
- Mercury(II) oxide decomposes upon heating to produce mercury (Hg) and oxygen gas (O2). The reaction is:
\[ 2HgO \rightarrow 2Hg + O2 \]

3. **Conclusion**:
- From the analysis, we find that both silver oxide (Ag2O) and mercury(II) oxide (HgO) decompose upon heating, while zinc oxide and aluminum oxide do not.
- Therefore, the metal oxides that decompose on heating are Ag2O and HgO.

### Final Answer:
The metal oxides which decompose on heating are **Ag2O (silver oxide)** and **HgO (mercury(II) oxide)**.

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