Question

Logan demonstrates to the class how mass must be conserved in every chemical reaction.

He measures the mass of hydrochloric acid and a magnesium strip separately. He then places the magnesium strip into the acid and bubbles form as the magnesium
seems to disappear. The combined mass afterward is less than the original.
Hydrochloric Acid + Magnesium
How could Logan explain this lower mass?

Answer 1

Logan could explain the lower mass by explaining that the reaction between hydrochloric acid and magnesium produces hydrogen gas, which escapes and therefore is not included in the final combined mass measurement. The reaction is:HCl + Mg → MgCl2 + H2Since the hydrogen gas has mass, its escape from the reaction vessel explains the decrease in the combined mass of the reactants after the reaction.