What is a Displacement Reaction?
A displacement reaction is the one wherein the atom or a set of atoms is displaced by another atom in a molecule. For instance, when Iron is added to a copper sulphate solution, it displaces the copper metal.
A + B-C → A-C + B
The above equation exists when A is more reactive than B.
A and B have to be either:
- Halogens where C indicates a cation.
- Different metals wherein C indicates an anion.
Single Displacement Reaction
A single displacement reaction which is also called as single replacement reaction is a kind of oxidation-reduction chemical reaction when an ion or element moves out of a compound, i.e., one element is replaced by the other in a compound.
- When chlorine is added in its gaseous form (or as a gas dissolved in water) to the solution of sodium bromide, the chlorine acquires the place of bromine. Since chlorine is more reactive than bromine, it displaces bromine from sodium bromide, and the solutions turn blue. The brown colour is the bromine that is displaced. If you notice the equation, you can see that the Cl and Br have swapped their original places.chlorine + sodium bromide → sodium chloride + bromine
Cl2(aq) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)
Let’s analyze another chemical reaction.
- Dissolve 0.5 gm of Silver nitrate in 10 ml of water in a test tube. A copper wire is then dipped in it and kept undisturbed for some time. The shining silver crystals are visible on the Copper wire. The solution becomes bluish as some amount of copper is developed. In the below reaction, the copper metal displaces silver from Silver Nitrate solution.Cu(s) + 2AgNo3(aq) → 2Ag(s) + Cu(NO3)2(aq)
Double Displacement Reaction
Double displacement reactions occur when a part of two ionic compounds are exchanged and make two new components. The pattern of a double displacement reaction is like this.
Double displacement reactions take place mostly in aqueous solutions wherein the ions precipitate, and exchange of ions takes place.
For example, when a solution of barium chloride is mixed with sodium sulphate, a white precipitate of barium sulphate is formed rapidly. These reactions are ionic in nature. The reactants get transformed into ions when dissolved in water and exchange of ions occur in the solution and results in the formation of a product molecule.
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