The reaction `CH_(4)+Cl_(2)underset("light")overset("hv")rarrCH_(3)Cl+HCl` is an example of

Options

A. additional reaction
B. substitution reaction
C. elimination reaction
D. oxidation reaction

Explanation

To solve the question regarding the reaction \( CH_4 + Cl_2 \xrightarrow{hv} CH_3Cl + HCl \), we need to analyze the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are methane (\( CH_4 \)) and chlorine gas (\( Cl_2 \)).
- The products are chloromethane (\( CH_3Cl \)) and hydrochloric acid (\( HCl \)).

2. **Understand the Reaction Conditions**:
- The reaction occurs in the presence of light (indicated by \( hv \)). This suggests that the reaction is initiated by light energy, which is often necessary for reactions involving free radicals.

3. **Analyze the Type of Reaction**:
- In this reaction, one hydrogen atom from methane (\( CH_4 \)) is replaced by a chlorine atom from chlorine gas (\( Cl_2 \)).
- This process involves the breaking of a bond (the C-H bond in methane) and the formation of a new bond (the C-Cl bond in chloromethane).

4. **Define the Mechanism**:
- The reaction proceeds through a free radical mechanism. When the chlorine molecules absorb light, they dissociate into two chlorine free radicals (\( Cl \cdot \)).
- These free radicals can then react with methane, leading to the substitution of a hydrogen atom with a chlorine atom.

5. **Conclusion**:
- Since one atom (hydrogen) is being replaced by another atom (chlorine), this type of reaction is classified as a **substitution reaction**.

### Final Answer:
The reaction \( CH_4 + Cl_2 \xrightarrow{hv} CH_3Cl + HCl \) is an example of a **substitution reaction**.