Question

Ms. Block's students are studying chemical reactions. A classic reaction occurs when a metal is added to hydrochloric acid. Miguel and Kai added 30g of hydrochloric acid (HCl) to 30g of magnesium (Mg) in a large test tube; bubbles appeared, the test tube felt warm, and they could no longer see the magnesium. They found that the mass of the products of the reaction was 52g. Since the Law of Conservation of Matter stated that matter cannot be created or destroyed, they were puzzled about the difference in mass. What is the best explanation for the missing 8g?
Responses
A 8g of hydrogen gas escaped from the test tube.8g of hydrogen gas escaped from the test tube.
B 8g of magnesium disappeared during the reaction.8g of magnesium disappeared during the reaction.
C Miguel and Kai were not very proficient at using the beam balance.Miguel and Kai were not very proficient at using the beam balance.
D 8g of the mass produced the heat the boys felt at the end of the experiment.8g of the mass produced the heat the boys felt at the end of the experiment.

Answer 1

A 8g of hydrogen gas escaped from the test tube.

The chemical reaction between hydrochloric acid and magnesium produces hydrogen gas, which can easily escape from the test tube. This accounts for the missing 8g of mass.