Which of the following element (M) react with `HNO_3` to form `MO_2` ?

Options

A. `P_4`
B. Mg
C. Zn
D. Sn

Answer

To determine which element (M) reacts with HNO3 to form MO2, we will analyze the reactions of the given elements with nitric acid.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements we need to consider are P (Phosphorus), Mg (Magnesium), Zn (Zinc), and Sn (Tin).

2. **Reaction of P4 with HNO3**:
- When P4 reacts with HNO3, it forms H3PO4 (phosphoric acid), NO2 (nitrogen dioxide), and H2O (water).
- The reaction does not produce PO2 (phosphorus dioxide) as phosphorus primarily exists in +3 and +5 oxidation states. Therefore, PO2 is not stable and cannot be formed.
- **Conclusion**: P4 does not form MO2.

3. **Reaction of Mg with HNO3**:
- Magnesium reacts with nitric acid to form magnesium nitrate (Mg(NO3)2) and hydrogen gas (H2).
- No MgO2 (magnesium dioxide) is formed; instead, MgO (magnesium oxide) is the product.
- **Conclusion**: Mg does not form MO2.

4. **Reaction of Zn with HNO3**:
- Zinc reacts with nitric acid to produce zinc nitrate (Zn(NO3)2) and hydrogen gas (H2).
- ZnO (zinc oxide) is the oxide formed, not ZnO2.
- **Conclusion**: Zn does not form MO2.

5. **Reaction of Sn with HNO3**:
- Tin reacts with nitric acid to form tin oxide (SnO2), nitrogen dioxide (NO2), and water (H2O).
- Tin can exist in the +4 oxidation state, which allows it to form SnO2 (tin dioxide).
- **Conclusion**: Sn forms MO2.

6. **Final Answer**:
- Among the elements considered, only Tin (Sn) reacts with HNO3 to form MO2 (specifically SnO2).

### Answer:
The element (M) that reacts with HNO3 to form MO2 is **Tin (Sn)**.

---