Which of the following oxides is not expected to react with sodium hydroxide ?

Options

A. `B_(2)O_(3)`
B. `CaO`
C. `SiO_(2)`
D. `BaO`

Explanation

To determine which oxide is not expected to react with sodium hydroxide (NaOH), we need to analyze the nature of each oxide provided in the options: B2O3, CaO, SiO2, and BaO.

### Step-by-Step Solution:

1. **Identify the Nature of Each Oxide:**
- **B2O3 (Boron trioxide):** This is a non-metallic oxide and is acidic in nature. Acidic oxides typically react with bases like NaOH.
- **CaO (Calcium oxide):** This is a metallic oxide and is basic in nature. Basic oxides do not react with bases.
- **SiO2 (Silicon dioxide):** This is also a non-metallic oxide and is acidic in nature. It reacts with bases like NaOH.
- **BaO (Barium oxide):** This is a metallic oxide and is basic in nature. However, it can also react with strong bases under certain conditions.

2. **Determine the Reactivity with Sodium Hydroxide:**
- **B2O3 + NaOH:** Reacts to form sodium borate and water.
- **CaO + NaOH:** Does not react as both are basic.
- **SiO2 + NaOH:** Reacts to form sodium silicate and water.
- **BaO + NaOH:** Can react to form barium hydroxide, but it is also basic.

3. **Conclusion:**
- Among the given options, **CaO (Calcium oxide)** is the oxide that is not expected to react with sodium hydroxide because it is a basic oxide.

### Final Answer:
The oxide that is not expected to react with sodium hydroxide is **CaO**.

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