For every, 3 Br- ions, 1 Al3+ ion reacts to form AlBr3.
Convert 16.2g of aluminum to moles:
16.2g Al / 27.0g per mol = 0.60 mols.
Based on the above ratio, 0.60 mols of Al will react with 1.8 mols of Br.
Convert 1.8 mols of Br to its mass:
1.8 mols Br × 79.9g per mol = 143.82g of Br.
