Question

a student is told that both energy and mass must be conserved in every chemical reaction. she measures the mass of hydrochloric acid and a zinc strip. she drops the zinc strip into the acid and bubbles form as the zinc looks like it disappears. the combined mass afterward is less than before. which of the following can explain this result? a the student must have not measured the mass correctly. b the zinc disappears and therefore the mass is less after the reaction. c this is not a chemical reaction so the conservation laws do not apply. d the bubbles indicate that a gas is created and mass is lost as it escapes from the container.

Explanation:

In a chemical reaction, mass is conserved. When zinc reacts with hydrochloric acid, hydrogen gas is produced. If the reaction is not carried out in a closed - system, the gas escapes, making the measured combined mass after the reaction less. This is because the mass of the gas is not accounted for in the measurement.

Answer:

D. Gas escapes, indicating mass loss as it leaves the container.