Answer:
Last option C(s) + O2(g) → CO2(g)
Explanation:
The reactions are:
2Ca(s) + Cl2(g) → CaCl2(s)
4Mg(s) + O2(g) → 2MgO(s)
Li(s) + Cl2(g) → 2LiCl(s)
C(s) + O2(g) → CO2(g)
Let's count the atoms (check out the stoichiometry):
1. We have 2 Ca in reactant side and 2Cl, in product side we have 1 Ca and 2 Cl. UNBALANCED
2. We have 4 Mg in reactant side and 2 O. In product side we have 2 Mg and 2 O. UNBALANCED
3. In reactant side we have 1 Li and 2 Cl. Then, in product side we have 2Li and 2Cl. UNBALANCED
C(s) + O2(g) → CO2(g)
1 C and 2 O ⇒ 1 C and 2 O Correctly balanced
