Arrange the following oxides in decreasing acidic order
`SiO_(2)`   (I) `CO_(2)`(II)   `SO_(3)`(III)   `N_(2)O_(5)`(IV)

Options

A. ` III gt IVgt II gtI`
B. ` IV gt III gt II gt I`
C. `IV gt II gt III gtI`
D. ` III gt II gt IVgtI`

Answer

To arrange the oxides `SiO_(2)`, `CO_(2)`, `SO_(3)`, and `N_(2)O_(5)` in decreasing order of acidity, we need to analyze the acidic character of each oxide based on their position in the periodic table and their molecular structure.

### Step-by-Step Solution:

1. **Identify the Oxides**: We have four oxides to consider:
- `SiO_(2)` (Silicon dioxide)
- `CO_(2)` (Carbon dioxide)
- `SO_(3)` (Sulfur trioxide)
- `N_(2)O_(5)` (Dinitrogen pentoxide)

2. **Understand Acidic Character**: The acidic character of oxides generally increases as you move from left to right across a period and decreases as you move down a group in the periodic table. This is due to the effective nuclear charge and the size of the atoms.

3. **Analyze Each Oxide**:
- **`N_(2)O_(5)`**: This oxide is formed from nitrogen, which is in Group 15. It is a strong acid (nitric acid when dissolved in water), making it the most acidic among the listed oxides.
- **`SO_(3)`**: Sulfur trioxide is also a strong acid (sulfuric acid when dissolved in water) and is more acidic than the others except for `N_(2)O_(5)`.
- **`CO_(2)`**: Carbon dioxide is a weak acid (carbonic acid when dissolved in water) but is still more acidic than `SiO_(2)`.
- **`SiO_(2)`**: Silicon dioxide is amphoteric but behaves more like a weak acid, making it the least acidic of the four.

4. **Rank the Acidity**:
- **Most Acidic**: `N_(2)O_(5)` (IV)
- **Next**: `SO_(3)` (III)
- **Then**: `CO_(2)` (II)
- **Least Acidic**: `SiO_(2)` (I)

5. **Final Order**: Thus, the decreasing order of acidity for the oxides is:
- `N_(2)O_(5)` > `SO_(3)` > `CO_(2)` > `SiO_(2)`

### Final Answer:
The decreasing order of acidity for the oxides is:
`N_(2)O_(5)` > `SO_(3)` > `CO_(2)` > `SiO_(2)`