Assertion:Ethene on treating with `Br_2` in presence of NaCl forms `CH_2CICH_2Br` and `CH_2Br-CH_2-Br`
Reason:This addition involves the formation of free radicals

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion
B. If both assertion and reason are true but reason is not the correct explanation of the assertion
C. if assertion is true but reason is false
D. If the assertion and reason both are false

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that ethene (C₂H₄) reacts with bromine (Br₂) in the presence of sodium chloride (NaCl) to form two products: CH₂Cl-CH₂Br and CH₂Br-CH₂Br.

- When ethene reacts with Br₂, it undergoes an electrophilic addition reaction. The Br₂ molecule can add across the double bond of ethene.
- The presence of NaCl introduces chloride ions (Cl⁻) into the reaction, which can also participate in the addition reaction.
- The reaction can lead to the formation of two products:
1. CH₂Br-CH₂Br (1,2-dibromoethane)
2. CH₂Cl-CH₂Br (bromo-chloroethane)

Thus, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that this addition involves the formation of free radicals.

- The addition of Br₂ to alkenes typically involves the formation of a bromonium ion, not free radicals. The bromonium ion is a cyclic intermediate formed when Br₂ adds to the double bond.
- The attack of the bromide ion (Br⁻) or chloride ion (Cl⁻) on the bromonium ion leads to the formation of the final products.
- Therefore, the reason is **false** as it incorrectly describes the mechanism of the reaction.

### Conclusion
- The assertion is true because the products mentioned can indeed be formed.
- The reason is false because the mechanism involves the formation of a bromonium ion, not free radicals.

### Final Answer
The correct answer is that the assertion is true, but the reason is false.