Asample of the compound magnesium oxide is synthesized as follows. 60. g of magnesium is burned and produces 100. g of magnesium oxide, indicating that the magnesium combined with 40. g of oxygen in the air. if 30. g of magnesium had been used, what mass of oxygen would have combined with it? what law of chemistry is used in solving this problem?

30 g of magnesium would be combined with 20 g of oxygen. The law used solving this problem is the Lavoisier Law of conservation of mass.

Explanation:

If 60 g of magnesium combines with 40 g of oxygen to make 100 g of magnesium oxide, then 30 g of magnesium will combine with 20 g of oxygen to make 50 g of magnesium oxide.

This happens because in a chemical reaction there is no creation or descruction of atoms, only a rearrangement. Therefore, the mass of reactants should be equal to the mass of products.

The following equation represents the proportions of the substances:

Mg + 1/2O₂ → MgO