Difference Between Double Displacement and Acid Base Reactions

Double Displacement vs Acid Base Reactions
 

During a chemical reaction, all the reactants change their form and produce new compounds with new properties. There are various ways to detect whether a chemical reaction is taking place. For example, heating/ cooling, color change, gas production, and precipitate formation can be taken. There are many types of reactions, as well. Double displacement reactions and acid base reactions are two t such ypes.

What is Double Displacement Reaction?

These types of reactions are also known as double replacement reactions. When two compounds are reacting together, they exchange their positive and negative ions with each other. This type of reactions has the following general formula.

AB +CD → AD + BC

Usually AB and CD are ionic compounds. Therefore, in aqueous medium, they are in the form of ions (A⁺ and B^–, C⁺ and D^–). A and C are cations and B and D are anions. The cation of AB (that is A) forms a new compound with the anion of CD (that is D).  And this happens vice versa. So to conclude, a double displacement reaction is where cations and anions of two compounds switch their partners. There are three types of double displacement reactions as precipitation reactions, neutralization reactions and gas forming reactions. In precipitation reactions, one of the new compounds will be in the solid state. For example, we will take the reaction between silver nitrate (AgNO₃) and HCl. Ag⁺ and H⁺ are monovalent cations, and NO₃^– and Cl^– are monovalent anions. When these switch partners AgCl and HNO₃ are formed. From these two products, AgCl is a precipitate.

AgNO₃ + HCl → AgCl + HNO₃

As in the above example, all the cations and anions are monovalent. So when exchanging balanced equation can be automatically obtained. But if the valency is different in ions, the equations have to be balanced. And when writing the products, valency should be carefully considered. Take the following example. The cations are Fe ³⁺ and H⁺, whereas the anions are O₂^2- and Cl^–. Therefore, after writing the products, equation can be balanced as below.

Fe₂O₃ + 6 HCl  → 2 FeCl₃ + 3 H₂O

What is Acid Base Reaction?

We normally identify an acid as a proton donor. Acids can be categorized into two, based on their ability to dissociate and produce protons. Strong acids like HCl, HNO₃ are completely ionized in a solution to give protons. Weak acids like CH₃COOH are partially dissociates and give fewer amounts of protons. In the pH scale, from 1-6 represent acids. An acid with pH 1 is said to be very strong, and as the pH value increases, acidity is decreased.  Bases have a hydroxide anion and have the ability to donate it as a hydroxide ion to be a base. Acid base reactions are neutralization reactions. When an acid and a base react, a salt and water is formed. Water results from the combination of H⁺ ions forms the acid and OH^– ions from the base. Therefore, this is also a type of double displacement reaction.

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