Question

When magnesium metal (Mg) is burned, it forms MgO. How many moles of oxygen gas (O2) are needed to burn 20 moles of Mg? The balanced equation is:
2Mg + O2 --> 2MgO

Answer 1

First let me caution you that when Mg is BURNED IN OXYGEN the product is MgO. Burn it in N2) and the product will be Mg3N2.
2Mg + O2 --> 2MgO
If you have 20 mols Mg, you will need 20 mols Mg x (1 mol O2/2 mols Mg) = 20*1/2 = 10 mols O2.

Answer 2

When is the produced when mg is burned by oxtgen???