What is a displacement reaction?

• A. A reaction where a more reactive metal replaces a less reactive metal in a compound in solution.
• B. A reaction where a gas is produced.
• C. A color change reaction.
• D. A reaction with no energy change.

Answer: (A)

Displacement reactions involve a more reactive metal kicking out a less reactive metal from a compound in solution. The statement describes exactly that: when a metal that is higher in the reactivity series is placed into a solution containing ions of a less reactive metal, it replaces the less reactive metal in the compound, forming a new salt of the more reactive metal and freeing the less reactive metal. For example, zinc can displace copper from copper sulfate to form zinc sulfate and copper metal. This happens because zinc is more reactive and more readily loses electrons to reduce the copper ions.

The idea rests on the reactivity series: a displacement only occurs when the reacting metal is above the metal in the compound. Gas production, color change, or no energy change are not defining features of displacement reactions; they can occur in other types of reactions.