Question

How many moles of O2 are needed to form 3 moles of Al2O3 from the element

Answer 1

Well, you have 4Al + 3O2 = 2Al2O3, so you need 3 moles of O2 for every 4 moles of Al. So, for 3 moles of Al2O3, you need 6 moles of Al, so you need 3/4 * 6 = 9/2 moles of O2.

I think.