Which metal gives blue ash when it's salt is heated with `Na_(2)CO_(3)` solid and `Co(NO_(3))_(2)` on a charcoal piece?

Options

A. Cu
B. Mg
C. AI
D. Zn

Explanation

To determine which metal gives blue ash when its salt is heated with sodium carbonate (Na₂CO₃) and cobalt nitrate (Co(NO₃)₂) on a charcoal piece, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Reaction**: When metal salts are heated with sodium carbonate and cobalt nitrate on a charcoal piece, they undergo a reduction reaction. The cobalt nitrate acts as an oxidizing agent, and the sodium carbonate helps in the formation of metal oxides.

2. **Identify the Metals**: The question provides four options: Copper, Magnesium, Aluminum, and Zinc. We need to analyze each metal's behavior under the given conditions.

3. **Analyze Each Metal**:
- **Copper (Cu)**: When heated with sodium carbonate and cobalt nitrate, copper typically gives a brown residue. This does not match the blue ash requirement.
- **Magnesium (Mg)**: Magnesium does not give a colored residue in this test, so it can be ruled out.
- **Aluminum (Al)**: Aluminum is known to produce a blue ash when heated with sodium carbonate and cobalt nitrate. The reaction forms cobalt aluminate (CoAl₂O₄), which is blue in color.
- **Zinc (Zn)**: Zinc produces a green mass when subjected to the same test, which also does not match the blue ash requirement.

4. **Conclusion**: Based on the analysis, the metal that gives blue ash when its salt is heated with sodium carbonate and cobalt nitrate on a charcoal piece is Aluminum (Al).

### Final Answer:
The metal that gives blue ash is **Aluminum (Al)**.

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