At STP, how many liters of H2 can be made from the complete reaction of 12.5 grams of Al? (Only enter the number, NO UNITS, and round to the tenth place, 1 decimal)

Question

At STP, how many liters of H2 can be made from the complete reaction of 12.5  grams of Al? (Only enter the number, NO UNITS, and round to the tenth place, 1 decimal)

Given:    2 Al   +   6 HCl   →   2 AlCl3.  +   3 H2

Anonymous · Answer

Al is about 27 grams per mol
so we have 12.5 grams * 1 mol / 27 grams = 0.463 mols of Al
for every 2 mols of Al you get 3 mols of H2
so mols of H2 = (3/2) * 0.463 = 0.694 mols H2
at STP as I recall 22.4 liters holds a mol
0.694 mols * 22.4 liters / mol =15.6 liters