Aluminum wiring can be a fire hazard because it can oxidize, or combine with oxygen..
Well, aluminum oxide is Al2O3, right? So for every 2 aluminum atoms there are 3 oxygen atoms, So, if you have three moles of aluminum, you'll need 4 and a half moles of oxygen to react completely with the aluminum. One mole of oxygen atoms weighs 16 grams, so 4.5 moles weighs 72 grams, right? Now it could be that your teacher told you three point zero zero moles of aluminum to get you to use two significant figures, so if you've studied significant figures you may want to look up a more accurate number for the atomic weight of aluminum, and carry the calculation through to three significant figures. Otherwise, 72 is a fine answer.
