Question

how does a displacement reaction differ from a double displacement reaction? give examples to explain

Answer 1

those reaction in which one element takes the place of another element in a compound are known as displacement reaction
CuSO4 +Zn=ZnSO4+Cu

those reaction in which two compound react by an exchange of ions to form two new compound are double displacement reaction
NaOH+HCl =NaCl+H2O

Answer 2

Displacement Reaction:

1) Those reactions in which a more reactive element displaces a less active element from its compound are called displacement reactions.

2) Example - Reaction between Iron and Copper Sulphate Solution. When Iron [Fe] filings are added to Copper Sulphate solution [CuSO₄], The Iron displaces the Copper from the Copper Sulphate solution and forms Iron Sulphate [FeSO₄] and Copper is left out.  

Equation: Fe + CuSO₄ $\longrightarrow$ FeSO₄ + Cu  

Double-Displacement Reaction:

1) A reaction in which new compounds are formed by mutual exchange of ions between two compounds.

2) Example - Reaction between Sodium Sulphate and Barium Chloride.  

Equation: Na₂SO₄ + BaCl₂ $\longrightarrow$ BaSO₄ + 2NaCl.

White Precipitate of Barium Sulphate is formed. Hence this reaction is also called a Precipitate reaction.