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Definition of Precipitation Reaction and its Applications

A reaction is nothing but forming new substances when two or more reactants come into contact with each other. There are many forms of reactions like a combination, precipitation, decomposition reactions etc. A reaction is said to be precipitation if and only if it forms a precipitate in an aqueous solution. It is of two types:- single displacement and double displacement reaction.

These types of reactions have many uses. It is well applicable in the case of water purification and also identifying the presence of a specific element. The precipitation definition itself suggests that the reaction forms a precipitate of insoluble salt when combined with two ionic bonds. In this article, we will explain more about the reaction and its application.

Examples of a precipitation reaction

Silver nitrate and potassium chloride reactions are common examples of this reaction.

AgNO3(aqueous) + KCl(aqueous) → AgCl(precipitate) + KNO3(aqueous)

In this above reaction, silver chloride is precipitated out. Here two ionic aqueous solutions (aq) react to yield a solid product (s).

In terms of ion in the solution, the reaction can be rewritten as,

Ag+ (aq) + NO3(aq) + K+ (aq) + Cl(aq) → AgCl (s) + K+ (aq) + NO3(aq)

Other examples include:

  • 2KOH(aqueous) + CaCl2(aqueous)→ Ca(OH)2(aqueous) + 2KCl(aqueous)
  • AgNO3(aqueous) + NaCl(aqueous)→ AgCl↓ + NaNO3 (aqueous)
  • Mg(OH)2(s) + 2HCl (aqueous) → (aqueous) + 2H2O(l)

Properties of precipitation reaction

  • The reaction occurs in aqueous solutions or medium in an ionic state
  • The product is formed when the reaction take place between ions in the aqueous solution
  • The insoluble salts formed as the end product of the reaction are said to be precipitates
  • These reactions are also known as ionic reactions since the ions actively participate in the reaction and form the product.
  • Precipitation reaction depends on temperature, the concentration of the solution, buffer solution, etc.

Other types of reactions

Apart from the precipitation, there are many other types of reactions.

  • Combination reaction
  • Displacement reaction
  • Decomposition reaction
Types of Chemical Reactions Explanation General Reaction
Combination reaction Two or more compounds combine to form one mixture. A + B → AB
Decomposition reaction A decomposition reaction is a reaction in which the complex molecule breaks down to make simpler ones. AB → A + B
Displacement reaction A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution. A + Soluble salt B  → Precipitate + soluble salt C


Uses of a precipitation reaction

The first application of this reaction is, it is used to find the presence of a specific element in the given solution. The formation of the precipitate in the precipitation reaction determines it by adding some chemicals to the solution. They are also used in the extraction of magnesium from seawater.

When it comes to daily life, inside our body, the reaction between calcium ions and oxalic acid that are present in food results in calcium oxalate, which is a type of kidney stone. Another example is for the treatment of wastewater, some chemicals are added and thus the pollutants or impurities get precipitated out, which then allowed for the further purification process



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