chem help--- maximum mass obtained from this reaction?

Question

Lithium reacts with oxygen to make lithium oxide oxide. What is the maximum mass of lithium oxide (g) that could be prepared from 5.74 g of Li(s) and 13.73 g of O2(g)?

Answer 1

4Li + O2 ===> 2Li2O

Atomic weights: Li=7 O=16 O2=32 Li2O=30

5.74gLi x 1molLi/7gLi = 0.82 mole Li

13.73gO2 x1molO2/32gO2 = 0.43 mole O2

0.43 mole O2 would need 4 x 0.43 = 1.69 mole Li, and you don't have that. So Li is the limiting reagent (it runs out first). Getting back to Li:

0.82molLi x 2molLi2O/4molLi x 30gLi2O/1molLi2O = 12.3g Li2O