In the following reaction sequence -
(1) `ClrarrClrarroverset(•)(C )+overset(•)(C )l`
(2) `overset(•)(C )l+CH_(4)rarroverset(•)(C )H_(3)+HCl`
(3) `overset(•)(C )H_(3)+Cl_(2)rarrCH_(3)Cl+overset(•)(C )l`
(4) `overset(•)(C )H_(3)+overset(•)(C )H_(3)rarrCH_(3)-CH_(3)`
the termination step is -

Options

A. Reaction 1
B. Reaction 2
C. Reaction 3
D. Reaction 4

Answer

To identify the termination step in the given reaction sequence, we need to analyze each step carefully. The reactions provided are part of the chlorination of methane, which involves initiation, propagation, and termination steps. Let's break down the steps:

### Step-by-Step Solution:

1. **Identify the Reactions**:
- (1) `Cl• + Cl• → Cl2` (Initiation)
- (2) `Cl• + CH4 → CH3• + HCl` (Propagation)
- (3) `CH3• + Cl2 → CH3Cl + Cl•` (Propagation)
- (4) `CH3• + CH3• → CH3-CH3` (Termination)

2. **Understanding Each Step**:
- **Step 1** is the initiation step where chlorine radicals are formed from molecular chlorine (Cl2) under light.
- **Step 2** is a propagation step where a chlorine radical reacts with methane (CH4) to form a methyl radical (CH3•) and hydrochloric acid (HCl).
- **Step 3** is another propagation step where the methyl radical reacts with chlorine to form chloromethane (CH3Cl) and regenerate a chlorine radical.
- **Step 4** is the termination step where two methyl radicals combine to form ethane (CH3-CH3).

3. **Identifying the Termination Step**:
- The termination step is characterized by the combination of two radicals to form a stable product, which stops the chain reaction.
- In this case, the fourth reaction `CH3• + CH3• → CH3-CH3` represents the termination of the chain reaction as it results in the formation of a stable molecule (ethane) and consumes the radicals.

### Conclusion:
The termination step in the given reaction sequence is **Step 4: `CH3• + CH3• → CH3-CH3`**.