Which of the following oxides are basic ?

Options

A. `Mn_2O_7 and V_2O_3`
B. `V_2O_3 and CrO`
C. `CrO and Cr_2O_3`
D. `V_2O_5 and V_2O_3`

Explanation

To determine which of the given oxides are basic, we can follow these steps:

### Step 1: Identify the Oxides
We have the following oxides to analyze:
1. Mn2O7
2. V2O3
3. B2O3
4. CrO
5. Cr2O3
6. V2O5

### Step 2: Determine the Oxidation States
We will calculate the oxidation state of the metal in each oxide.

1. **Mn2O7**:
- Let the oxidation state of Mn be \( x \).
- The equation will be: \( 2x + 7(-2) = 0 \)
- Solving gives: \( 2x - 14 = 0 \) → \( x = +7 \)

2. **V2O3**:
- Let the oxidation state of V be \( x \).
- The equation will be: \( 2x + 3(-2) = 0 \)
- Solving gives: \( 2x - 6 = 0 \) → \( x = +3 \)

3. **B2O3**:
- Let the oxidation state of B be \( x \).
- The equation will be: \( 2x + 3(-2) = 0 \)
- Solving gives: \( 2x - 6 = 0 \) → \( x = +3 \)

4. **CrO**:
- Let the oxidation state of Cr be \( x \).
- The equation will be: \( x + (-2) = 0 \)
- Solving gives: \( x = +2 \)

5. **Cr2O3**:
- Let the oxidation state of Cr be \( x \).
- The equation will be: \( 2x + 3(-2) = 0 \)
- Solving gives: \( 2x - 6 = 0 \) → \( x = +3 \)

6. **V2O5**:
- Let the oxidation state of V be \( x \).
- The equation will be: \( 2x + 5(-2) = 0 \)
- Solving gives: \( 2x - 10 = 0 \) → \( x = +5 \)

### Step 3: Analyze Basicity
According to the rule:
- The higher the oxidation state, the more acidic the oxide.
- The lower the oxidation state, the more basic the oxide.

From our calculations:
- Mn2O7: +7 (acidic)
- V2O3: +3 (basic)
- B2O3: +3 (basic)
- CrO: +2 (basic)
- Cr2O3: +3 (basic)
- V2O5: +5 (acidic)

### Step 4: Conclusion
The oxides that are basic based on their oxidation states are:
- V2O3
- B2O3
- CrO
- Cr2O3

Thus, the basic oxides among the options provided are V2O3, B2O3, CrO, and Cr2O3.