What is the mass of MgO oxide obtained if 12 g of Mg reacts with O?

The combustion reaction of magnesium in oxygen is described by the following chemical reaction equation:
2Mg + O2 = 2MgO;
Let’s determine the molar mass of magic and its oxide:
M Mg = 24 grams / mol;
M MgO = 24 +16 = 40 grams / mol;
Let’s find the amount of substance in 12 grams of magnesium:
N Mg = 12/24 = 0.5 mol;
Find the mass of 0.5 mol of magnesium oxide:
m = 0.5 x 40 = 20 grams;