Question

write this in 7th grade level please Copper (Cu) reacts with sulfur (S) to form copper sulfide as shown in the equation. A scientist adds 12.7 grams of Cu to 3.2 grams 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 to be a total of 15.9 grams of copper sulfide (Cu2​S).

In 1–2 sentences, explain the law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide

Answer 1

The scientist used the Law of Conservation of Mass, which says matter cannot be created or destroyed in a chemical reaction. So the mass of the product must equal the mass of the reactants: 12.7 g + 3.2 g = 15.9 g.