How do you account for the formation of ethane during chlorination of methane ?

Explanation

Chlorination of methane is a free radical reaction which occurs by the following mechanism
(i) Chain initiation

(ii) Chain propagation `CH_(4)+overset(*)(Cl) to overset(*)(CH_(3))+ HCl`
`overset(*)(CH_(3))+ + Cl- Cl to CH_(3)Cl+ overset(*)(Cl)`
Chain termination `overset(*)(CH_(3))+overset(*)(CH_(3)) to underset("ethane") (CH_(3)- CH_(3))`
`overset(*)(CH_(3))+overset(*)(Cl) to CH_(3)Cl`
`overset(*)(Cl) +overset(*)(Cl) to Cl_(2)`
It is clear from the above mechanism, that the free radical `CH_(3)` may combine with itself to form ethane molecule.