Question: determine how many moles of o2 are required to react completely?
Answer: You need to balance the equation and see the mole ratio between the reactants. For this equation, the mole ratio is 3 moles of O2 : 4 moles of Al. So, you would then multiply: 14.8 moles*(3/4) = 11.1 moles. 11.1 moles O2 are needed to react completely with 14.8 moles of Al.