Zinc reacts with hydrochloric acid to produce hydrogen gas because zinc is more reactive than hydrogen and can displace it from the acid. Copper, on the other hand, does not react with hydrochloric acid because it is less reactive than hydrogen and cannot displace it. This difference in reactivity is reflected in their positions in the reactivity series of metals.
Elaboration:
Reactivity Series:
The reactivity series of metals arranges metals in order of their reactivity, with the most reactive metals at the top and the least reactive metals at the bottom. In this series, zinc is positioned above hydrogen, while copper is positioned below hydrogen.
Displacement Reaction:
When a more reactive metal reacts with a solution containing a less reactive metal ion, the more reactive metal displaces the less reactive metal ion from the solution.
Zinc and Hydrochloric Acid:
Zinc is more reactive than hydrogen, so when zinc reacts with hydrochloric acid (HCl), the zinc atoms displace the hydrogen ions (H+) from the acid, forming hydrogen gas (H2) and zinc chloride.
Copper and Hydrochloric Acid:
Copper is less reactive than hydrogen, so it cannot displace the hydrogen ions from the acid. Therefore, no reaction occurs between copper and hydrochloric acid.