Consider the reaction: 4 Al + 3O2 --> 2 Al2O3 How many moles of Al2O3 are produced when 13 moles of Al reacts?

Answer 1

4 Al + 3O2 --> 2 Al2O3

The balanced equation shows that half as many moles of Al2O3 are produced as there are starting moles of Al.

Therefore, if you begin with 13 moles of Al, you will end up with 6.5 moles of Al2O3.