The reaction in which an atom or a set of atoms are displaced by another atom in a molecule is called displacement reaction. For instance, when Iron is added to a copper sulfate solution, it displaces the copper metal.
A + B – C → A – C + B
The above equation exists when A is more reactive than B.
The reaction in which two atoms or a group of atoms are displaced by another atom in a molecule is called a double displacement reaction.
A-B + C-D → A-C + B-D
A and B have to be either:
- Halogens where C indicates a cation.
- Different metals wherein C indicates an anion.
The difference between displacement reaction double displacement reaction is tabulated below:
|Single Displacement reaction||Double displacement reaction|
|In a displacement reaction, a more reactive element replaces a less reactive element from a compound.||In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.|
|In a displacement reaction, one displacement takes place.
A + BX → AX + B
|In a double displacement reaction, two displacements take place to complete the reaction.
AB + CD → AC + BD
|Change in color takes place with no precipitate forms.||Precipitate is formed.|
|Metals react with the salt solution of another metal.||Salt solutions of two different metals react with each other.|
2KI + Cl2 → 2KCl + I2 is a displacement reaction.
CuSO4 + Zn → ZnSO4 + Cu is also a displacement reaction.
Na2SO4 + BaCl2 → BaSO4 + 2NaCl is a double displacement reaction.
2KBr + BaCl2 → 2KCl + BaBr2 is also a double displacement reaction.