Calculate the amount of Oxygen required to react with 12 g of mangia.

Let’s write the reaction equation:

2Mg + O2 = 2MgO

Let’s find the amount of magnesium substance:

v (Mg) = m (Mg) / M (Mg) = 12/24 = 0.5 (mol).

According to the reaction equation, 2 mol of Mg reacts with 1 mol of O2, therefore:

v (O2) = v (Mg) / 2 = 0.5 / 2 = 0.25 (mol).

Thus, the required volume of oxygen, measured under normal conditions:

V (O2) = v (O2) * Vm = 0.25 * 22.4 = 5.6 (l).

Answer: 5.6 l.