So confused! please help where do i even start?

Question

Aluminum oxide is formed from its elements

4AL 3O2 --> 2Al2 O3

How many grams of Al will react with 12.0 L O2 at STP?

Answer 1

At STP 1 mole of gas= 22.4 liters, so 12 liters= 0.54 moles

4 moles of Al will react with 3 moles of O2, so set up the ratio

4/3= x/0.54, where x= moles of aluminum

x= 0.72 moles

Atomic weight of Al is 27 gm/mole

gms of Al= 0.72 moles * 27 gm/mol= 19.4 gms

Answer 2

12 L of O2 - how many moles? That's your start.