Arrange the correct sequence for mechanism of chlorination of methane.
I. `CH_(4)+Cl^(*) overset(hv)rarroverset(*)CH_(3)+H-Cl`
II. `Cl-Cl overset(hv)rarr 2overset(*)Cl`
III. `overset(*)CH_(3)+Cl_(2)rarrCH_(3)-Cl+Cl^(*)`
(IV) `overset(*)Cl+overset(*)Cl rarrCl-Cl`
`overset(*)CH_(3)+overset(*)CH_(3) rarr CH_(3)-CH_(3)`
Choose the correct option is

Options

A. II, I, III and IV
B. I, II, III and IV
C. IV, III, II and I
D. II, III, I and IV

Answer

To arrange the correct sequence for the mechanism of chlorination of methane, we need to understand the steps involved in the reaction. The chlorination of methane involves three main stages: initiation, propagation, and termination. Let's break down the steps provided in the question:

1. **Step II**: `Cl-Cl overset(hv)rarr 2overset(*)Cl`
- This step represents the initiation phase where chlorine molecules (Cl2) are broken down into two chlorine radicals (Cl*). This occurs in the presence of UV light (hv).

2. **Step III**: `overset(*)CH_(3)+Cl_(2)rarrCH_(3)-Cl+Cl^(*)`
- This step is part of the propagation phase. The chlorine radical reacts with methane (CH4) to form chloromethane (CH3Cl) and another chlorine radical (Cl*).

3. **Step I**: `CH_(4)+Cl^(*) overset(hv)rarroverset(*)CH_(3)+H-Cl`
- This step is also part of the propagation phase. Here, the chlorine radical (Cl*) abstracts a hydrogen atom from methane (CH4), forming a methyl radical (CH3*) and hydrogen chloride (HCl).

4. **Step IV**: `overset(*)Cl+overset(*)Cl rarrCl-Cl`
- This step represents the termination phase where two chlorine radicals combine to form a chlorine molecule (Cl2), effectively terminating the chain reaction.

Now, let's arrange these steps in the correct order:

- **Initiation**: Step II (Cl-Cl → 2Cl*)
- **Propagation**: Step III (CH3* + Cl2 → CH3Cl + Cl*)
- **Propagation**: Step I (CH4 + Cl* → CH3* + HCl)
- **Termination**: Step IV (Cl* + Cl* → Cl2)

Thus, the correct sequence is: II, III, I, IV.

### Final Answer:
The correct order is: II, III, I, IV.