Question

If an atom or a group of atoms replace another atom or a group of atoms during a chemical change, then it is called:

• A. chemical combination reaction
• B. chemical displacement reaction
• C. photochemical reaction
• D. chemical decomposition reaction

Answer 1

Answer: (B)

chemical displacement reaction

Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals participate in displacement reactions. A metal placed higher in the activity series can displace the metal that occupies a lower position from the aqueous solution of its salt.

In single displacement reactions, elements that form cations can only displace cations and elements that form anions can only displace anions.

$Mg\left(s\right)+CuS{O}_4\left(aq\right)\to MgS{O}_4\left(aq\right)+Cu\left(s\right)$

A strip of Mg metal is placed in a copper sulphate solution, the blue colour of copper sulphate disappears and the Mg metal turns brown, as the displaced copper is deposited on it.