The number of amphoteric oxides among `Cr_2O_3, V_2O_5,CrO, Mn_2O_7, NiO, Fe_2O_3, Mn_3O_4, VO_2, Cu_2O, MnO_2, CrO_2 ` is

Explanation

To determine the number of amphoteric oxides among the given compounds, we will analyze each oxide based on its chemical properties and the oxidation states of the metals involved.

### Step-by-Step Solution:

1. **Understanding Amphoteric Oxides**:
Amphoteric oxides are those that can react both as acids and bases. Typically, these oxides are formed by metals that have intermediate oxidation states.

2. **List of Given Oxides**:
The oxides given are:
- Cr₂O₃
- V₂O₅
- CrO
- Mn₂O₇
- NiO
- Fe₂O₃
- Mn₃O₄
- VO₂
- Cu₂O
- MnO₂
- CrO₂

3. **Analyzing Each Oxide**:
- **Cr₂O₃**: Chromium is in the +3 oxidation state. This oxide is amphoteric.
- **V₂O₅**: Vanadium is in the +5 oxidation state. This oxide is amphoteric.
- **CrO**: Chromium is in the +2 oxidation state. This oxide is basic.
- **Mn₂O₇**: Manganese is in the +7 oxidation state. This oxide is acidic.
- **NiO**: Nickel is in the +2 oxidation state. This oxide is basic.
- **Fe₂O₃**: Iron is in the +3 oxidation state. This oxide is amphoteric.
- **Mn₃O₄**: This is a mixed oxide (Mn in +3 and +4 states). This oxide is amphoteric.
- **VO₂**: Vanadium is in the +4 oxidation state. This oxide is amphoteric.
- **Cu₂O**: Copper is in the +1 oxidation state. This oxide is amphoteric.
- **MnO₂**: Manganese is in the +4 oxidation state. This oxide is amphoteric.
- **CrO₂**: Chromium is in the +4 oxidation state. This oxide is amphoteric.

4. **Counting the Amphoteric Oxides**:
From the analysis:
- Amphoteric oxides: Cr₂O₃, V₂O₅, Fe₂O₃, Mn₃O₄, VO₂, Cu₂O, MnO₂, CrO₂
- Total amphoteric oxides = 8

### Final Answer:
The number of amphoteric oxides among the given compounds is **8**.