2 Mg + O2 --> 2MgO What is the greatest amount of MgO (in moles) that can be made with 7.8 moles of Mg and 4.7 moles of O2? First, convert 7.8 mol Mg to mol MgO. How many moles of MgO are produced with 7.8 mol of Mg? (Answer a numerical value only)