How many grams of magnesium and oxygen does it take to make 10g of magnesium oxide?

Decision:

Let’s write the reaction equation for the interaction of magnesium with oxygen
2Mg + O2 = 2MgO;

The relative atomic mass of magnesium is 24, oxygen is 16. This means that the molecular weight of magnesium oxide is 40 g / mol.
Let’s find the amount of substance in magnesium oxide:
10/40 = 0.25 mol;

Magnesium has the same coefficient as magnesium oxide. This means that the amount of substance in magnesium is 0.25 mol. Let’s find the mass of magnesium:
24 * 0.25 = 6 grams;

There is a factor 2 times lower before oxygen than before magnesium oxide. This means that the amount of substance in oxygen is 0.125 mol. Let’s find the mass of oxygen:
32 * 0.125 = 4 grams;

Answer: the mass of magnesium is 6 grams, the mass of oxygen is 4 grams.