Use the chemical equation to complete the activity. copper (cu) reacts with sulfur (s) to form copper sulfide as shown in the equation. A scientist adds 12.7 g of (CU) 3.2 g of (S) 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 grams of copper sulfide (Cu2S). In 1-2 sentences, explain the law that the scientist use to predict that the product of the reaction would be 15.9 g of copper sulfide