Copper reacts with sulfur to form copper sulfide as shown in the equation a scientist adds 12.7 g of copper to 3.2 g of sulfur to start the reaction in this reaction. All of the copper and all of the sulfur react before running the experiment, the scientist expected the products of the reaction will be a total of 15.9 g of copper sulfide, in one to two sentences, explain the law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide

The law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide is the Law of Conservation of Mass, which states that the mass of the reactants must be equal to the mass of the products in a chemical reaction.