Conjugate Acid Base Pairs

Lemon juice, vinegar, and ant bites all have one thing in common; they are acids. On the other hand, daily use objects like soaps, detergents, and toothpaste also have one thing in common; they are all bases. Acids and bases surround us everywhere we go. The reaction between acids and bases is crucial for a lot of phenomena around us. 

There are many concepts of what acids and bases are, and one of the important ones is the Lowry Bronsted theory of acids and bases. Much of chemistry focuses on the transfer of electrons as the key to identifying bases and acids but the Lowry Bronsted theory uses protons to describe what acids and bases are.

Lowry Bronsted Theory

Developed by the independent endeavours of two scientists, the Lowry Bronsted Theory is a new way of looking at chemicals. Danish scientist Johannes Nicolaus Bronsted and English scientist Thomas Martin Lowry are credited with coming up with a way that describes a chemical reaction as the transfer of a proton and not an electron. It laid the foundation to expand what constituted an acid and what constituted a base. It also helped in classifying certain special entities like cations, anions and neutral molecules into acids and bases. It hinges on the fact that an acid cannot function without a base, and similarly, a base cannot function without an acid.

Lowry Bronsted Acids and Bases

According to the Lowry Bronsted scheme of acids and bases, acids are described as any entity that can donate a proton in a reaction. To understand this, let us first have a look at what protons are. All atoms are made up of neutrons, electrons and protons. If in an atom we remove all the electrons, we will be left with only the protons and neutrons and since neutrons have no charge, we would effectively have only a positively charged atom with protons. 

In the Lowry Bronsted concept, a proton refers to the H+ ion. This is because hydrogen has only a proton and an electron. Upon removing all the electrons, the only charged particle remaining in hydrogen will be the proton, and therefore, the H+ ion is also referred to as a proton. The Lowry Bronsted concept focuses on the transfer of protons in any reaction. Thus, a compound that can transfer a proton is called an acid, and a compound that can receive a proton is called a base.

Conjugate Acid Base Pairs

Any reaction that occurs in nature very rarely occurs in one go. Instead, most reactions happen in intermediate steps that take place one after the other. Some of these intermediate steps may be fast and some infinitesimally slow. The Lowry Bronsted concept also views reactions in terms of half-reactions that involve the transfer of protons.

According to the Lowry Bronsted Concept, an acid is a proton donor. Therefore, it loses a proton and gains a negative charge. But in doing so, the acid itself forms a new entity that can accept a proton back. This means that upon losing a proton, the acid gets converted into a new base. This base is called a conjugate base of the acid.

Similarly, when a base takes part in a chemical reaction, it gains a proton. This means that after the reaction, the base becomes a proton-rich species. A proton-rich species can donate protons, and therefore, is a Lowry Bronsted acid. Hence, after partaking in a reaction, a base becomes a conjugate acid.

Conjugate acids and bases are couples that occur in any reaction and are a direct result of the transfer of protons. This is because the transfer of protons changes the charge on the species, and hence, alters their classification as an acid or a base.

Examples of a reaction

Conclusion

Developed by the independent endeavours of two scientists, the Lowry Bronsted Theory is a new way of looking at chemicals. Danish scientist Johannes Nicolaus Bronsted and English scientist Thomas Martin Lowry are credited with coming up with a way that describes a chemical reaction as the transfer of a proton and not an electron.

According to the Lowry Bronsted Concept, an acid is a proton donor. But in doing so, the acid itself forms a new entity that can accept a proton back. This means that upon losing a proton, the acid gets converted into a new base. This base is called a conjugate base of the acid.

Similarly, when a base takes part in a chemical reaction, it gains a proton. This means that after the reaction, the base becomes a proton-rich species. A proton-rich species can donate protons, and therefore, is a Lowry Bronsted acid. Hence after partaking in a reaction, a base becomes a conjugate acid.