What is the difference between displacement and double displacement reactions ? Write equations for these reactions.

In a displacement reaction, a more reactive element replaces a less reactive element from a compound.

$A + BX \longrightarrow AX + B$;   where $A$ is more reactive than $B$

In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.

$AB + CD \longrightarrow AD + CB$

For example :

Displacement reaction :

$CuS{O_{4(aq)}}\, + \,Z{n_{(s)}}\, \to \,ZnS{O_{4(aq)}}\, + \,C{u_{(s)}}\,$

Double displacement reaction :

$N{a_2}S{O_{4(aq)}}\, + \,BaC{l_2}_{(aq)}\, \to \,BaS{O_{4(s)}}\, + \,2NaC{l_{(aq)}}\,$