posted by Alejandra .
How many grams of bromine are required to react completely with 37.4 grams aluminum chloride?
Actually, the reaction you're proposing will not occur; however, here is how you work the problem.
2AlCl3 + 3Br2 ==> 2AlBr3 + 3Cl2
mols AlCl3 = grams/molar mass
Convert mols AlCl3 to mols Br2 using the coefficients in the balanced equation.
Convert mols Br2 to g. g = mols x molar mass.