Ethylene reacts with ozone gas to form the compound

Options

A. HCHO
B. `C_2H_5OH`
C.
D. `CH_3CHO`

Explanation

### Step-by-Step Solution:

1. **Identify the Reactants**:
- We start with ethylene, which has the molecular formula \( C_2H_4 \) or \( CH_2=CH_2 \).
- The other reactant is ozone, represented as \( O_3 \).

2. **Reaction with Ozone**:
- When ethylene reacts with ozone, it undergoes a reaction known as ozonolysis.
- The double bond in ethylene reacts with ozone to form an intermediate compound called an ozonide.

3. **Formation of Ozonide**:
- The reaction leads to the formation of ethylene ozonide, which can be represented as:
\[ CH_2-CH_2 + O_3 \rightarrow \text{Ethylene ozonide} \]
- This intermediate compound contains three oxygen atoms.

4. **Hydrolysis of Ozonide**:
- The ozonide then undergoes hydrolysis when treated with water (\( H_2O \)).
- During hydrolysis, the ozonide breaks down to form carbonyl compounds.

5. **Formation of Formaldehyde**:
- The ozonide reacts with water to yield two molecules of formaldehyde (\( HCHO \)):
\[ \text{Ethylene ozonide} + H_2O \rightarrow 2 HCHO \]
- Here, formaldehyde is the final product of the reaction.

6. **Final Product**:
- The final compound formed from the reaction of ethylene with ozone followed by hydrolysis is formaldehyde, which has the formula \( HCHO \).

### Conclusion:
- The compound formed when ethylene reacts with ozone gas is **formaldehyde (HCHO)**.