First of all, we must write our reaction:
2Al + 3Cl2 => 2AlCl3 (don't forget to balance it)
The limiting reactant:
We work with stoichiometry,
2 x 1 mole Al --------- 3 x 1 mol Cl2
5.4 moles Al ------- x
x = 8.1 moles
According to this result, for 5.4 moles of Al, we need 8.1 moles of Cl2, but we have 80 moles, so CL2 is the excess reactant.
The limiting reactant = Al
The excess reactant = Cl2
Grams of AlCl3 produced procedure:
The molar mass of AlCl3 = 133 g/mol
2 x 1 mole Al --------- 2 x 133 g AlCl3
5.4 moles Al ---------- y = 718.2 g
Answer:
The excess reactant = Cl2
Grams of AlCl3 = 718.2 g