The binary compounds of oxygen with other elements are called oxides. They are classified depending either upon their acid-base characteristics or on the basis of oxygen content.
(a) Normal oxides : These oxides which contain oxygen atom as permitted by the normal oxidation number, i.e., `-2` normal oxide may be acidic, basic, amphoteric or neutral.
(b) Polyoxides : The oxides which contain oxygen atoms different than those permitted by the normal oxidation number of `-2`.
(i) Peroxides : Two oxygen atoms are linked to each other and oxyegen has `-1` oxidation number. They contain `(O -O)^(2-)` unit.
(ii) Superoxodes : These oxides contain `(O-O)^(-1)` unit, i.e., each O-atom has oxidation number `-1//2`.
(c) Suboxides : These contain low content of oxygen than expected.
(d) Mixed oxides : These oxides are made of two simpler oxides.
Which of the following pairs contains neutral oxides ?

Options

A. `SO_2, SO_3`
B. `N_2 O_3, N_2 O_5`
C. `CO, NO`
D. `Na_2 O, CaO`

Answer

To determine which of the given pairs contains neutral oxides, we need to understand the characteristics of neutral oxides and analyze the options provided.

### Step-by-Step Solution:

1. **Definition of Neutral Oxides**:
- Neutral oxides are oxides that do not exhibit acidic or basic properties. They do not react with acids or bases and do not change the color of litmus paper.

2. **Analyzing the Options**:
- We need to evaluate each pair of oxides to see if they are neutral.

3. **Option A: Sulfur Dioxide (SO₂) and Sulfur Trioxide (SO₃)**:
- Both SO₂ and SO₃ are known to be acidic oxides. They react with water to form acids (H₂SO₃ and H₂SO₄, respectively).
- **Conclusion**: This pair does not contain neutral oxides.

4. **Option B: Nitrogen Trioxide (N₂O₃) and Nitrogen Pentoxide (N₂O₅)**:
- N₂O₃ and N₂O₅ are also acidic oxides. N₂O₃ forms nitric acid when reacted with water, and N₂O₅ forms a stronger nitric acid.
- **Conclusion**: This pair does not contain neutral oxides.

5. **Option C: Carbon Monoxide (CO) and Nitrogen Monoxide (NO)**:
- Both CO and NO are classified as neutral oxides. They do not react with acids or bases and do not change the color of litmus paper.
- **Conclusion**: This pair contains neutral oxides.

6. **Option D: Oxides of Group 1 and Group 2 Elements**:
- These oxides are generally basic in nature. For example, sodium oxide (Na₂O) and magnesium oxide (MgO) react with acids to form salts and water.
- **Conclusion**: This pair does not contain neutral oxides.

### Final Answer:
The pair that contains neutral oxides is **Option C: Carbon Monoxide (CO) and Nitrogen Monoxide (NO)**.

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