Which of the following oxides is least basic in nature ?

Options

A. CrO
B. `Cr_(2)O_(3)`
C. `CrO_(3)`
D. `Cr_(2)O_(4)`

Answer

To determine which of the given oxides is least basic in nature, we need to analyze the oxidation states of chromium in each oxide and understand how oxidation state affects basicity.

### Step-by-Step Solution:

1. **Identify the Oxides**: The oxides given in the question are:
- CrO
- Cr2O3
- CrO3
- Cr2O4

2. **Determine the Oxidation State of Chromium in Each Oxide**:
- For **CrO**:
- Let the oxidation state of Cr be \( x \).
- The equation is: \( x + (-2) = 0 \) (since oxygen has an oxidation state of -2).
- Solving gives: \( x = +2 \).

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

- For **CrO3**:
- Let the oxidation state of Cr be \( x \).
- The equation is: \( x + 3(-2) = 0 \).
- Solving gives: \( x - 6 = 0 \) → \( x = +6 \).

- For **Cr2O4**:
- Let the oxidation state of Cr be \( x \).
- The equation is: \( 2x + 4(-2) = 0 \).
- Solving gives: \( 2x - 8 = 0 \) → \( x = +4 \).

3. **Summarize the Oxidation States**:
- CrO: +2
- Cr2O3: +3
- CrO3: +6
- Cr2O4: +4

4. **Analyze Basicity**:
- Basicity of metal oxides generally decreases with increasing oxidation state. This means that the lower the oxidation state, the more basic the oxide is.
- Therefore, the basicity order from least to most basic based on oxidation states is:
- CrO3 (+6) < Cr2O4 (+4) < Cr2O3 (+3) < CrO (+2)

5. **Conclusion**:
- Since CrO has the lowest oxidation state (+2), it is the most basic. Conversely, CrO3 has the highest oxidation state (+6), making it the least basic.
- Thus, the oxide that is least basic in nature is **CrO3**.

### Final Answer:
The least basic oxide among the given options is **CrO3**.