Which of the following compounds are not base when dissolved?

Options

A. `K_(2)O`
B. `Na_(2)O_(2)`
C. `NO_(2)`
D. `Cl_(2)O_(7)`

Answer

To determine which of the given compounds do not produce a base when dissolved in water, we will analyze each compound's reaction with water step by step.

### Step 1: Identify the Compounds
The compounds given in the question are:
1. K2O (Potassium oxide)
2. Na2O2 (Sodium peroxide)
3. NaO2 (Sodium oxide)
4. Cl2O7 (Dichlorine heptoxide)

### Step 2: Analyze Each Compound's Reaction with Water

**1. K2O (Potassium oxide)**
- When K2O is dissolved in water, it reacts as follows:
\[ K2O + H2O \rightarrow 2KOH \]
- KOH (Potassium hydroxide) is a strong base because it contains OH⁻ ions.

**2. Na2O2 (Sodium peroxide)**
- When Na2O2 is dissolved in water, it reacts as follows:
\[ Na2O2 + 2H2O \rightarrow 2NaOH + H2O2 \]
- Here, NaOH (Sodium hydroxide) is produced, which is a strong base, along with H2O2 (Hydrogen peroxide), which is a weak acid.

**3. NaO2 (Sodium oxide)**
- When NaO2 is dissolved in water, it reacts as follows:
\[ NaO2 + H2O \rightarrow HNO3 + HNO2 \]
- This reaction produces HNO3 (Nitric acid) and HNO2 (Nitrous acid), both of which are acids and do not produce a base.

**4. Cl2O7 (Dichlorine heptoxide)**
- When Cl2O7 is dissolved in water, it reacts as follows:
\[ Cl2O7 + H2O \rightarrow 2HClO4 \]
- HClO4 (Perchloric acid) is produced, which is a strong acid and does not produce a base.

### Step 3: Conclusion
From the analysis:
- K2O produces a strong base (KOH).
- Na2O2 produces a strong base (NaOH).
- NaO2 produces acids (HNO3 and HNO2).
- Cl2O7 produces a strong acid (HClO4).

Thus, the compounds that do not produce a base when dissolved in water are **NaO2** and **Cl2O7**.

### Final Answer
The compounds that are not bases when dissolved are:
- **NaO2**
- **Cl2O7**

---