CH4 + 10 Cl2 → CCl4 + 4 HCl4
This is an oxidation-reduction (redox) reaction:
C-IV - 8 e- → CIV (oxidation)
4 HI - 12 e- → 4 HIV (oxidation)
20 Cl0 + 20 e- → 20 Cl-I (reduction)
CH4 is a reducing agent, CH4 is a reducing agent, Cl2 is an oxidizing agent.