Nitrate is converted into metal oxide on heating. This metal is:

Options

A. `Li`
B. `Na`
C. `Mg`
D. (1) and (3) both

Answer

To determine which metal nitrate converts into a metal oxide upon heating, we can analyze the thermal decomposition of various metal nitrates.

### Step-by-Step Solution:

1. **Identify the Nitrates**: We need to consider the nitrates of different metals. Common examples include lithium nitrate (LiNO3), sodium nitrate (NaNO3), and magnesium nitrate (Mg(NO3)2).

2. **Thermal Decomposition of Lithium Nitrate**:
- When lithium nitrate (LiNO3) is heated, it decomposes as follows:
\[ 2 \text{LiNO}_3 \rightarrow \text{Li}_2\text{O} + 2 \text{NO}_2 + \frac{1}{2} \text{O}_2 \]
- This reaction produces lithium oxide (Li2O), which is a metal oxide.

3. **Thermal Decomposition of Sodium Nitrate**:
- Sodium nitrate (NaNO3) decomposes upon heating:
\[ 2 \text{NaNO}_3 \rightarrow 2 \text{NaNO}_2 + \text{O}_2 \]
- This reaction does not produce a metal oxide; it produces sodium nitrite (NaNO2) instead.

4. **Thermal Decomposition of Magnesium Nitrate**:
- Magnesium nitrate (Mg(NO3)2) decomposes as follows:
\[ 2 \text{Mg(NO}_3\text{)}_2 \rightarrow 2 \text{MgO} + 4 \text{NO}_2 + \text{O}_2 \]
- This reaction produces magnesium oxide (MgO), which is also a metal oxide.

5. **Conclusion**: From the analysis, both lithium nitrate and magnesium nitrate produce metal oxides (Li2O and MgO respectively) upon heating. Therefore, the metals that fit the criteria of the question are lithium and magnesium.

6. **Final Answer**: The correct answer is that the metal is either lithium (Li) or magnesium (Mg). If the options provided include both, select the one that is asked for. If only one option is provided, choose that option.