Question

If 18.80 grams of hydrochloric acid are reacted with a large amount of aluminum metal, what volume of hydrogen gas would be produced at STP? (Hint: start by writing a balanced equation for the reaction.)

3HCl + Al -> 3H + AlCl3
18.80g
moles= grams/mw
18.80/109.5
0.1716894977169

I do not know if I have correctly balanced the equation, and I think I need to use PV=NRT somewhere, but I'm not sure how to get there.

Answer 1

2Al + 6HCl ==> 3H2 + 2AlCl3
One error you continue to make is to determine mole from the entire equation. moles = grams/molar mass. and NOT grams/n*molar mass.
Here is a worked example of a stoichiometry problem. Just follow the steps. That will show you how to do moles, too.
http://www.jiskha.com/science/chemistry/stoichiometry.html