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

(N/A) The chlorination of methane proceeds via a free radical mechanism involving initiation,propagation,and termination steps.
In the termination step,two methyl free radicals $(CH_3^{\bullet})$ collide and combine to form ethane $(C_2H_6)$.
$CH_3^{\bullet} + CH_3^{\bullet} \rightarrow CH_3-CH_3$