Calculate the amount of magnesium oxide substance obtained by burning magnesium with a mass of 12 grams.

Let’s write the reaction equation:

2Mg + O2 (t) = 2MgO

The amount of magnesium substance:

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

According to the reaction equation, from 2 moles of Mg, 2 moles of MgO are formed, therefore:

v (MgO) = v (Mg) = 0.5 (mol).

Thus, the amount of the substance of the formed magnesium oxide:

v (MgO) = 0.5 (mol).

Answer: 0.5 mol.