Final answer:
According to the Law of Conservation of Mass, the total mass before and after a chemical reaction must be the same. Since no mass is lost, the mass in the Ziploc bag after the reaction will remain at 45.0 g. The correct option is C.
Step-by-step explanation:
The question is related to the Law of Conservation of Mass, which states that in a chemical reaction, mass is neither created nor destroyed. The initial mass of compounds A and B is 25.0 g and 20.0 g respectively, making the total mass 45.0 g.
During the reaction in the Ziploc bag, these compounds will react to form new substances, but the overall mass in the bag after the reaction is over will remain the same, assuming that no gases escape from the bag.
Therefore, the answer is C. 45.0 g, because the sum of the masses of the reactants will equal the sum of the masses of the products according to the Law of Conservation of Mass. The correct option is C.