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

Displacement reaction:

(a) When a more reactive element displaces a less reactive element from its salt solution, In displacement reaction one displacement takes place. it is called displacement reaction.
(b) In displacement reaction one displacement takes place.

Double Displacement reaction:

(a) There is an exchange of ions between the reactants to produce new substances, it is called double displacement reaction.
(b) In double displacement reaction two displacements takes place.
Following are examples of Displacement reaction and Double Displacement reaction.

Displacement reaction

$$ Mg(s) + 2HCl(aq) \rightarrow MgCl_{2} + H_{2}(g) $$

Double Displacement reaction

$$ \;\;\; 2KBr(aq) + BaCl_{2} $$

$$ \downarrow$$

$$ \;\;\; 2KCl(aq) + BaBr_{2}$$