Precipitation Reaction – Definition and Examples

Precipitation Reaction

A precipitation reaction is a chemical reaction that occurs in aqueous solution and form precipitates. Further, chemical reactions consist of chemical changes that take place within the substances. Thus, it gives rise to a new element under some particular conditions.

Moreover, chemical reactions occur between two or more chemical compounds that we refer to as reactants. Thus, the reactants can be in forms of solid, gas or liquid.

What is Precipitation Reaction?

It means the chemical reaction occurs in aqueous solutions where two ions bond together to form insoluble salts.

These insoluble salts formed are precipitates that are the products of it. They can be single displacement reactions or double displacement reactions.

In a double displacement reaction, both ionic reactants dissociate in water and their ions bonds with the respective cation or anion from the other reactant.

For a double displacement reaction to be a precipitation reaction, one of the resulting products must be insoluble in aqueous solution.

In a single replacement reaction, one ionic compound dissociates. Thus, either its cation or anion starts bonding with another ion in solution. In order to form an insoluble product.

Precipitation Reaction Equation

The chemical reaction between potassium chloride (KCl) and silver nitrate (AgNO₃), and solid silver chloride (AgCl) is the precipitate or the insoluble salt formed as a product of the reaction is one of the examples of a precipitation reaction. The equation of the reaction

AgNO₃(aqueous) + KCl(aqueous) —–AgCl(precipitate) + KNO₃(aqueous)

In the reaction of potassium chloride and silver nitrate, results in the formation of silver chloride(AgCl) which is a white precipitate in a solid-state and insoluble in water.

With the help of precipitation reactions, we can determine the presence of different ions present in a particular solution.

Examples of Precipitation Reaction

Some examples are reaction between calcium chloride (CaCl₂) and potassium hydroxide(KOH), resulting in the formation of calcium hydroxide that is an insoluble salt.

The reaction between silver nitrate (AgNO₃) and sodium chloride (NaCl), results in the formation of silver chloride (AgCl) that is an insoluble salt.

The reaction between magnesium hydroxide (Mg(OH)₂) and hydrochloric acid (HCl), resulting in the formation of magnesium chloride(MgCl₂) that is an insoluble salt. The chemical equation for these reactions are

2KOH(aqueous) + CaCl₂(aqueous)—-Ca(OH)₂(aqueous) + 2KCl(aqueous)

AgNO₃(aqueous) + NaCl(aqueous) —- AgCl↓ + NaNO₃ (aqueous)

Mg(OH)₂(s) + 2HCl (aqueous) ——— MgCl₂(aqueous) + 2H₂O(l)

In our daily life, we can use it in wastewater treatment. When a contaminant creates an insoluble solid. It thus allows us to use this reaction for precipitating out the ions that are contaminated.

In wastewater, heavy metals are present such as compounds of sulfide and hydroxide. Thus, we can add a source of hydroxide that is soluble (NaOH Or Na₂S) which result in it and form a precipitate of impurities.

Properties of Precipitation Reaction

• The reactants should be in aqueous solutions or medium in an ionic state.

• It takes place between ions of the reactants present in the aqueous solutions, which form the product.

• At the end of it, the products which form are the precipitates that are insoluble in aqueous solutions.

• They are known as ionic reactions because by the exchange of ions in the reaction, the product is formed.

Applications of Precipitation Reaction

We can determine the presence of a particular element in the given solution with the help of precipitation reaction.

When we add some chemical into solutions, precipitation reaction helps in monitoring the formation of a precipitate in the solution.

These are used for the extraction of magnesium from the seawater. In the human body reaction between antigens and antibodies is a precipitation reaction.

Solved Question for You

Q: What are the types of precipitation?

Ans: The different kinds of precipitation are rain, snow, sleet, and hail. Some sources include freezing rain as the fifth type of precipitation.