Final answer:
According to the Law of Conservation of Mass, the total mass in the Ziploc bag after the reaction is the sum of the masses of compound A and compound B, which is 45.0 g.
Step-by-step explanation:
The mass of the Ziploc bag after the reaction between compounds A and B can be determined by using the Law of Conservation of Mass, which states that in a chemical reaction, matter is neither created nor destroyed. According to this principle, if compounds A and B react in a closed system, like a Ziploc bag, the total mass of the system must remain the same before and after the reaction. Therefore, the mass of compound A (25.0 g) combined with the mass of compound B (20.0 g), equals a total mass of 45.0 g, which will be the mass in the Ziploc bag after the reaction. The answer is B) 45.0 g.