Calculate the volume of oxygen. Required for combustion 12g Mg.

1. Let’s compose the equation of the chemical reaction:

2Mg + O2 = 2MgO.

2. Find the chemical amount of burned magnesium:

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

3. Using the reaction equation, we find the chemical amount of oxygen, and then its volume

Vm – molar volume, constant equal to 22.4 l / mol):

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

V (O2) = n (O2) * Vm = 0.25 mol * 22.4 L / mol = 5.6 L.

Answer: V (O2) = 5.6 liters.