How much oxygen is needed to burn 24 g of magnesium?

The equation for the reaction of magnesium with oxygen:

2Mg + O2 = 2MgO

The amount of magnesium substance:

v (Mg) = m (Mg) / M (Mg) = 24/24 = 1 (mol).

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

v (O2) = v (Mg) / 2 = 1/2 = 0.5 (mol).

Thus, the volume of oxygen that reacts with magnesium and measured at normal conditions:

V (O2) = v (O2) * Vm = 0.5 * 22.4 = 11.2 (l).

Answer: 11.2 l.