We'll begin by balancing the equation. This can be achieved by doing the following:
Fe + Cl2 —> FeCl3
There are 2 atoms of Cl on the left side and 3 atoms on the right side. It can be balance by putting 3 in front of Cl2 and 2 in front of FeCl3 as shown below:
Fe + 3Cl2 —> 2FeCl3
There are 2 atoms of Fe on the right side and 1 atom on the left side. It can be balance by putting 2 in front of Fe as shown below:
