`C_2 H_4 + H_2 to C_2H_6`. This reaction is

Options

A. addition
B. substitution
C. dissociation
D. decomposition

Explanation

To determine the type of reaction represented by the equation \( C_2H_4 + H_2 \rightarrow C_2H_6 \), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are ethene (\( C_2H_4 \)) and hydrogen (\( H_2 \)).
- The product is ethane (\( C_2H_6 \)).

2. **Analyze the Reaction Type**:
- In this reaction, two reactants (ethene and hydrogen) combine to form a single product (ethane).

3. **Define the Reaction Types**:
- **Addition Reaction**: This occurs when two or more reactants combine to form a single product.
- **Substitution Reaction**: This involves one atom or group being replaced by another in a compound.
- **Dissociation Reaction**: This involves breaking down a compound into its ions or simpler molecules.
- **Decomposition Reaction**: This involves breaking down a compound into two or more simpler substances without forming charged particles.

4. **Determine the Correct Type**:
- Since \( C_2H_4 \) and \( H_2 \) combine to form \( C_2H_6 \), this fits the definition of an addition reaction, where two reactants combine to form a single product.

5. **Conclusion**:
- Therefore, the reaction \( C_2H_4 + H_2 \rightarrow C_2H_6 \) is classified as an **addition reaction**.

### Final Answer:
The reaction \( C_2H_4 + H_2 \rightarrow C_2H_6 \) is an **addition reaction**.

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