Suppose you designed an experiment in which you burned a known quantity of magnesium in air. You used the product to determine how many moles of oxygen would react with the known number of moles of magnesium. Why would burning magnesium in air cause a source of error for this calculation?

Answer 1

Because Mg combines with N2, also in the air, to form Mg3N2. So although most of the product would be MgO, it would be contaminated with some Mg3N2.