The Reactivity Series
The key is the reactivity series of metals. This series ranks metals from most reactive to least reactive.
* Magnesium (Mg) is a more reactive metal than Copper (Cu). This means magnesium has a greater tendency to lose electrons and form positive ions.
The Reaction with Hydrochloric Acid
* Magnesium + Hydrochloric Acid (HCl) → Magnesium Chloride (MgCl₂) + Hydrogen Gas (H₂)
In this reaction:
* Magnesium (Mg) reacts with hydrochloric acid (HCl) to form magnesium chloride (MgCl₂) and hydrogen gas (H₂).
* The hydrogen ions (H⁺) in the acid are reduced to hydrogen gas by the magnesium.
* Magnesium loses electrons and forms magnesium ions (Mg²⁺), which combine with chloride ions (Cl⁻) to form magnesium chloride (MgCl₂).
Copper's Inactivity
* Copper + Hydrochloric Acid (HCl) → No Reaction
Copper is less reactive than hydrogen. It cannot displace hydrogen from hydrochloric acid. As a result, no reaction occurs.
Summary
Magnesium can react with hydrochloric acid because it is more reactive than hydrogen and can displace it. Copper, being less reactive, cannot displace hydrogen and therefore does not react with hydrochloric acid.
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