Among the oxides gives below, how many are acidic ? `CrO_3, Mn_2 O_7, CO, SO_2`.

Explanation

To determine how many of the given oxides are acidic, we will analyze each oxide based on its chemical composition and oxidation state of the central atom.

### Step 1: Analyze each oxide

1. **CrO₃ (Chromium trioxide)**:
- Chromium (Cr) has an oxidation state of +6 in CrO₃.
- Oxides of metals in high oxidation states (like +6) are typically acidic.
- **Conclusion**: CrO₃ is acidic.

2. **Mn₂O₇ (Manganese heptoxide)**:
- Manganese (Mn) has an oxidation state of +7 in Mn₂O₇.
- Similar to CrO₃, oxides of metals in high oxidation states (like +7) are also acidic.
- **Conclusion**: Mn₂O₇ is acidic.

3. **SO₂ (Sulfur dioxide)**:
- Sulfur (S) has an oxidation state of +4 in SO₂.
- Non-metal oxides are generally acidic, and SO₂ is an oxide of a non-metal (sulfur).
- **Conclusion**: SO₂ is acidic.

4. **CO (Carbon monoxide)**:
- Carbon (C) has an oxidation state of +2 in CO.
- CO is considered neutral; it does not exhibit acidic or basic properties.
- **Conclusion**: CO is neutral.

### Step 2: Count the acidic oxides
From the analysis above, we found:
- CrO₃: Acidic
- Mn₂O₇: Acidic
- SO₂: Acidic
- CO: Neutral

Thus, the total number of acidic oxides among the given options is **3** (CrO₃, Mn₂O₇, and SO₂).

### Final Answer
**3 oxides are acidic: CrO₃, Mn₂O₇, and SO₂.**

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