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 separately. She then places the zinc strip into the acid and bubbles form as the zinc looks like it disappears. The combined mass afterward is less than the original. Which of these 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 loss as it escapes from the container.

Answer 1

the bubbles indicate that a gas is being created therefore d is you answer

Answer 2

Hello!

The statement that can explain the result is The bubbles indicate that a gas is created and mass is lost as it escapes from the container.

The reaction between Hydrochloric Acid and a Zinc Strip is the following one:

2HCl (aq) + Zn (s)→ ZnCl₂(aq) + H₂(g)

The bubbles that the student sees are caused by the Hydrogen gas that is being formed in the reaction. If the container isn't hermetically sealed, the gas will escape the solution and the final mass will be lower than the original. However, if the container is sealed, measuring the final mass will prove the Law of Conservation of Mass.

Have a nice day!