How many grams of Al2O3 are produced when 50.3g of Al reacts?

Answer 1

find the moles of Al ... (sample mass) / (molar mass)

find moles of O reacted ... three moles of O for every two moles of Al
... (3/2) * (moles Al) = (moles O)

find mass of O reacted ... (moles O) * (molar mass O)

add the mass of O to the mass of Al

Answer 2

4 Al + 2 O3 -> 2 Al2O3