The chemical equation for the reaction between magnesium (Mg) and hydrochloric acid (HCl) is shown: Mg + 2HCI → MgCI2 + H2. Stacy initially weighs both the magnesium and hydrochloric acid, registering a combined mass of 55 grams. Subsequently, post-reaction, she assesses the mass of the resultant products, magnesium chloride (MgCl2) and hydrogen (H2), and once more records a total mass of 55 grams. Does Stacy's data substantiate the law of conservation of matter, and if so, what is the rationale behind this assertion?

Answer 1

Yes, Stacy's data substantiates the law of conservation of matter. This law states that matter cannot be created or destroyed in a chemical reaction; rather, the total mass of the reactants must equal the total mass of the products.

In Stacy's experiment, she initially measures the mass of magnesium (Mg) and hydrochloric acid (HCl) before the reaction, which totals 55 grams. When the reaction occurs, magnesium reacts with hydrochloric acid to form magnesium chloride (MgCl2) and hydrogen gas (H2). After the reaction, she measures the total mass of the products—magnesium chloride and hydrogen—and finds it also totals 55 grams.

The rationale behind this assertion lies in the fact that both the amount of magnesium and hydrochloric acid used in the reaction corresponds to the total mass of the products formed. According to the balanced chemical equation provided (Mg + 2HCl → MgCl2 + H2), all atoms in the reactants (Mg and HCl) are accounted for in the products (MgCl2 and H2). This confirms that there has been no loss or gain of mass during the reaction.

Thus, since the initial total mass of the reactants equals the final total mass of the products, Stacy’s observations strongly support the law of conservation of matter in her chemical reaction.