Which of the following oxides of Cr is amphoteric.

Options

A. `CrO_2`
B. `Cr_2O_3`
C. `CrO_5`
D. `CrO_3`

Explanation

To determine which of the oxides of chromium (Cr) is amphoteric, we need to analyze the oxidation states of each oxide and their behavior in acidic and basic environments.

### Step-by-Step Solution:

1. **Identify the Oxides of Chromium**: The oxides given are CrO2, Cr2O3, CrO5, and CrO3.

2. **Determine the Oxidation States**:
- For **CrO2**: Chromium has an oxidation state of +4.
- For **Cr2O3**: Chromium has an oxidation state of +3.
- For **CrO5**: Chromium has an oxidation state of +6.
- For **CrO3**: Chromium has an oxidation state of +6.

3. **Classify the Oxides**:
- Oxides with higher oxidation states (like CrO5 and CrO3) tend to be acidic because they do not have available electrons to donate.
- CrO2, with a +4 oxidation state, is also acidic due to its higher oxidation state.

4. **Analyze Cr2O3**:
- Cr2O3 has a +3 oxidation state. This oxide can react with both acids and bases.
- When Cr2O3 reacts with an acid (like HCl), it forms chromium chloride (CrCl3).
- When Cr2O3 reacts with a base (like NaOH), it forms sodium chromate (Na2CrO4) or dichromate (Cr2O7).

5. **Conclusion**: Since Cr2O3 can react with both acids and bases, it is classified as an amphoteric oxide. Therefore, the answer is **Cr2O3**.

### Final Answer:
The amphoteric oxide of chromium is **Cr2O3**.

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