Bronsted – Lowry and Lewis and their ionization

The proton hypothesis of acids and bases is also known as the Bronsted–Lowry theory. The Danish chemist Johannes Nicolaus Bronsted and the English chemist Thomas Martin Lowry separately proposed this hypothesis in 1923, claiming that any substance that can transmit a proton to another component is an acid, and any compound that accepts the proton is a base. A proton is a radioactive particle with a positive electrical charge unit. It is symbolised by the sign H⁺ since it is the nucleus of a hydrogen atom.

Concerning the Hypothesis

According to the Bronsted Lowry scheme, a substance only behaves as an acid in the presence of a base, and a substance only acts as a base in the presence of an acid. Furthermore, when an acidic material lacks a proton, it forms an acid called the acid conjugate base, and when a basic substance gains a proton, it forms an acid called the base conjugate acid. As a result, the reaction between an acidic material, such as hydrochloric acid, and a basic substance, such as ammonia, can be described as follows:

⁺NH₃NH₄⁺+Cl⁻ H ⇌+NH₃NH₄⁺+HCl⁻

The ammonium ion (NH₄⁺) is the acid conjugate of the base ammonia, and the chloride ion (Cl⁻) is the base conjugate of hydrochloric acid in the equation above.

The Bronsted–Lowry hypothesis also broadens the definition of acids and bases to include not just neutral molecules (such as alkali metal hydroxides and nitric, sulfuric, and acetic acids), but also molecules and atoms with positive and negative electrical charges (called as cations and anions). Acids include the hydronium ion, the ammonium ion, and various hydrated metal cations. Bases include the phosphate, acetate, sulphide, carbonate, and halogen ions.

Acids and Bases Definitions

Acids are chemicals that dissociate in an aqueous solution to form H⁺ (hydrogen ions), while bases are substances that dissociate in an aqueous solution to form OH, according to the Arrhenius theory (hydroxide ions).

In 1923, physical scientists Thomas Martin Lowry of England and Johannes Nicolaus Bronsted of Denmark proposed the theory that bears their names. This Bronsted Lowry theory represents acids and bases in terms of how they react with one another, allowing for greater generality. The equilibrium expression is used to express this definition.

combining acid and base conjugate acid + conjugate base = conjugate acid + conjugate base = conjugate acid + conjugate base = conjugate acid

Because the reaction can occur in both forward and backward directions, the equilibrium sign () can be employed. To become its conjugate base, A, the HA acid can lose a proton. B, the base, can receive a proton and convert to HB⁺, the conjugate acid. Because most acid-base reactions are rapid, the components of the reaction are usually in dynamic equilibrium with one another.

Aqueous Substances

Consider the acid-base reaction shown below:

CH₃COOH+H₂O⇌CH₃COO⁻+H₃O⁺

Acetic acid (CH₃COOH) is acid because it donates a proton to water (H₂O) and forms the acetate ion (CH₃COO), which is its conjugate base. Because it receives a proton from CH₂COOH and converts to its conjugate acid, the hydronium ion (H₃O⁺), H₂O is used as a base.

The acid-base reverse reaction is an acid-base reaction involving the acid’s conjugate base and the base’s conjugate acid in the initial reaction. In the example above, acetate is used as the reverse reaction’s base, and the hydronium ion is used as the acid.

H₃+⁺CH₃COO⁻⇌CH₃COOH+H₂O

Unlike Arrhenius’ hypothesis, Bronsted-theory Lowry’s has the advantage of not requiring acid to dissociate.

Comparison of the Lewis Acid-Base Theory 

1. N. Lewis developed an alternative/substitutional theory of acid-base reactions the same year Bronsted and Lowry published their theory. The electrical structure is the basis for Lewis’ theory. A Lewis base is a molecule that can contribute an electron pair to a Lewis acid. A Lewis acid, on the other hand, can take an electron pair. Lewis’ proposal uses the electrical structure to explain the Bronsted–Lowry categorisation.

HA+B⇌A⁻+BH⁺

In the above illustration, both the conjugate basis, A-, and the nucleus, B, are depicted containing a lone pair of electrons, namely the proton, which is a Lewis acid that can be transmitted between them.

Conclusion 

So we conclude that Brønsted-Lowry theory, also called proton theory of acids and bases, a theory, introduced independently in 1923 by the Danish chemist Johannes Nicolaus Brønsted and the English chemist Thomas .A Bronsted-Lowry acid is a compound that can donate a hydrogen ion while a Bronsted-Lowry base is a compound that can accept a hydrogen ion. A Lewis base is a compound that can donate a pair of electrons while a Lewis acid is a compound that can accept a pair of electrons.