To balance this chemical equation, we have to make sure that equal number of elements are located on the left side and the right side by placing coefficients:
CCl4 + O2 <-- --> COCl2 + Cl2
Balancing this equation:
2CCl4(g)+ O2(g) ⇌ 2COCl2(g) + 2Cl2(g)
Answer:
2,1,2,2