Which of the following compound on heating does not produce metal oxide?

Options

A. `MgCl_(2)*6H_(2)O`
B. `K_(2)Cr_(2)O_(7)`
C. `K_(2)CO_(3)`
D. `Cu(NO_(3))_(2)`

Explanation

To solve the question "Which of the following compounds on heating does not produce metal oxide?", we will analyze each of the given compounds and their reactions when heated.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- MgCl₂·6H₂O (Magnesium chloride hexahydrate)
- K₂Cr₂O₇ (Potassium dichromate)
- K₂CO₃ (Potassium carbonate)
- Cu(NO₃)₂ (Copper(II) nitrate)

2. **Analyze the First Compound (MgCl₂·6H₂O)**:
- When heated, magnesium chloride hexahydrate decomposes to form magnesium oxide (MgO), hydrochloric acid (HCl), and water (H₂O).
- **Reaction**:
\[ \text{MgCl}_2 \cdot 6\text{H}_2\text{O} \rightarrow \text{MgO} + \text{HCl} + \text{H}_2\text{O} \]
- **Conclusion**: This produces a metal oxide (MgO), so this is not the correct choice.

3. **Analyze the Second Compound (K₂Cr₂O₇)**:
- When potassium dichromate is heated, it decomposes to form potassium chromate (K₂CrO₄), chromium(III) oxide (Cr₂O₃), and oxygen (O₂).
- **Reaction**:
\[ \text{K}_2\text{Cr}_2\text{O}_7 \rightarrow \text{K}_2\text{CrO}_4 + \text{Cr}_2\text{O}_3 + \text{O}_2 \]
- **Conclusion**: This produces a metal oxide (Cr₂O₃), so this is not the correct choice.

4. **Analyze the Third Compound (K₂CO₃)**:
- Potassium carbonate does not decompose when heated; instead, it melts without producing any metal oxide.
- **Conclusion**: Since it does not produce any metal oxide upon heating, this is a potential correct choice.

5. **Analyze the Fourth Compound (Cu(NO₃)₂)**:
- When copper(II) nitrate is heated, it decomposes to form copper(II) oxide (CuO), nitrogen dioxide (NO₂), and oxygen (O₂).
- **Reaction**:
\[ 2\text{Cu(NO}_3\text{)}_2 \rightarrow 2\text{CuO} + 4\text{NO}_2 + \text{O}_2 \]
- **Conclusion**: This produces a metal oxide (CuO), so this is not the correct choice.

6. **Final Conclusion**:
- The only compound that does not produce a metal oxide upon heating is **K₂CO₃ (Potassium carbonate)**. Thus, the correct answer is option 3.