Acids, Bases and Salts as Electrolytes: Electrolytes are substances that produce ions when dissolved in water. Because they all produce ions when dissolved in water, they can be separated into acids, bases, and salts. Because the positive and negative ions, known as cations and anions, are mobile in these solutions, they conduct electricity. When strong electrolytes are dissolved, they completely ionise, and no neutral molecules form in the solution. When weak electrolytes dissolve in water, a small fraction of their molecules ionises. Their solutions contain some neutral compounds. Scroll down to learn more about acids, bases, and salts as electrolytes.

Definitions of Acids, Bases and Salts

Acids, bases, and salts were previously identified through the examination of their aqueous solutions. A substance that tastes sour in water turns blue litmus red and neutralises bases is known as an acid. If a substance’s aqueous solution tastes bitter, turns red litmus blue, or neutralises acids, it’s called a base. Salt is a neutral material that has no effect on litmus in an aqueous solution. Electrolytes, according to Faraday, are acids, bases, and salts. In addition, Liebig postulated that acids are hydrogen-containing molecules that metals can replace.

Acids

Acidity is a feature that distinguishes acids. Acidic chemicals are typically bitter. Aside from hydrochloric acid, there are a variety of different acids in our environment. Citric and ascorbic acids are found in citrus fruits like lemons and oranges, while tartaric acid is found in tamarind paste.

The words ‘acid’ and ‘acidity’ come from the Latin word ‘acidus,’ which means sour. A blue litmus paper will turn red when dipped in acid, whereas a red litmus paper would not change colour. When acids react with certain metals, they release dihydrogen.

Bases

The red litmus paper turns blue, but the blue litmus paper remains blue. They have a harsh taste and a soapy texture. Sodium bicarbonate, which is used in cooking, and household bleach are two further examples of bases.

Salts

Apart from sodium chloride, other frequent salts are sodium nitrate, barium sulphate, and potassium chloride. The interaction between hydrochloric acid (acid) and sodium hydroxide produces sodium chloride, also known as common salt (base). Electrostatic forces hold a cluster of positively charged sodium ions and negatively charged chloride ions together in solid sodium chloride.

Learn About Diazonium Salts Here

The dielectric constant of the medium is inversely proportional to electrostatic forces between opposite charges. In other words, a chemical with acidity in its nature and a compound with basicity in its nature can mix to form salts.

The dielectric constant of water, the universal solvent, is \(80.\) When sodium chloride is dissolved in water, the electrostatic force is reduced by the dielectric constant of water, allowing the ions to movely in the solution. Due to hydration with water molecules, they are also well-separated.

Ionisation And Dissociation

When a solid ionic substance dissolves in water, dissociation occurs, resulting in the separation of ions from an ionic crystal. Ionisation, on the other hand, is the process by which a neutral molecule dissolves in a solution and breaks into charged ions. The strength of ion-ion bonding and the extent of ion solvation determine the extent of ionisation.

The three most important modern concepts of acids and bases are:

Arrhenius Concept

Acids are substances that produce \({{\text{H}}^ + }\) ions when dissolved in water, while bases are substances that ionise in water to form \({\text{O}}{{\text{H}}^ – }\) ions, according to the Arrhenius idea.
\({\text{HA}} \to {{\text{H}}^ + } + {{\text{A}}^ – }\left({{\text{Acid}}} \right)\)
\({\text{BOH}} \to {{\text{B}}^ + } + {\text{O}}{{\text{H}}^ – }\left({{\text{Base}}} \right)\)
Acid-base reactions, according to Arrhenius, are characterised by acids dissociating in an aqueous solution to form hydrogen ions \(\left({{{\text{H}}^ + }} \right)\) and bases dissociating in an aqueous solution to form hydroxide \(\left({{\text{O}}{{\text{H}}^ – }} \right)\) ions. The number of \({{\text{H}}^ + }\) ions given by acid is known as the basicity of acid, and the number of \({\text{O}}{{\text{H}}^ – }\) ions given by base is known as the acidity of the base.

Limitations of Arrhenius Concept

1. Acids and bases require the presence of water to function correctly. \({\text{HCl}}\) can’t be used as an acid when it’s dry. Only water, not any other solvent, reacts with \({\text{HCl}}\) as an acid.
2. The concept doesn’t explain why compounds in non-aqueous solvents are acidic or basic.
3. Although reactions involving salt production can occur in the absence of a solvent, the neutralisation process is only conceivable for reactions that can occur in aqueous solutions.
4. Some salts, such as \({\text{AlC}}{{\text{l}}_3},\) have an acidic property in the aqueous solution that cannot be explained.
5. To define the basic nature of \({\text{N}}{{\text{H}}_3},\) a lengthy, as well as artificial explanation is required.

Bronsted-Lowry Concept

In \(1923,\) Bronsted and Lowry developed a more comprehensive concept of acids and bases. An acid is defined as any hydrogen-containing material (molecule, anion, or cation) that may donate a proton to another substance, while a base is defined as any substance (molecule, cation, or anion) that can absorb a proton from another substance, according to them. Acids, on the other hand, are proton donors, while bases are proton acceptors.

Conjugate Acid-Base Pairs

Consider a reaction:

\({\text{Aci}}{{\text{d}}_1} + {\text{Bas}}{{\text{e}}_2} \to {\text{Aci}}{{\text{d}}_2} + {\text{Bas}}{{\text{e}}_1}\)
\({{\text{H}}_2}{\text{O}} + {\text{HCl}} \to {{\text{H}}_3}{{\text{O}}^ + } + {\text{C}}{{\text{l}}^ – }\)
\({\text{HCl}}\) donates a proton to \({{\text{H}}_2}{\text{O}}\) in this process, making it an acid. Water, on the other hand, is a base because it accepts a proton from \({\text{HCl}}.\) The \({{\text{H}}_3}{{\text{O}}^ + }\) ions transfer a proton to the \({\text{C}}{{\text{l}}^ – }\) ion in the reverse process, which at equilibrium proceeds at the same rate as the forward reaction, making \({{\text{H}}_3}{{\text{O}}^ + }\) an acid. \({\text{C}}{{\text{l}}^ – }\) ion is a base because it receives a proton from the \({{\text{H}}_3}{{\text{O}}^ + }\) ion.

Conjugate acid-base pairs are acid-base pairs in which the members of a reaction can be created from each other by the gain or loss of protons.

Limitations of Bronsted Lowry Concept

1. Bronsted Lowry was unable to explain the reaction that took place in non-protonic solvents such as \({\text{COC}}{{\text{l}}_3},{\text{S}}{{\text{O}}_2},{{\text{N}}_2}{{\text{O}}_4},\) and others.
2. It can’t explain reactions between acidic oxides like etc. and basic oxides like etc., which can happen even when there’s no solvent present, e.g. (No proton transfer)
3. Although substances such as \({\text{B}}{{\text{F}}_3},{\text{AlC}}{{\text{l}}_3},\) and others lack hydrogen and hence are unable to contribute a proton, they still behave as acids.

Lewis Concept

Bases provide pairs of electrons to acids, whereas acids absorb pairs of electrons, according to Lewis’ theory of acid-base reactions. As a result, a Lewis acid can be described as an electron-pair acceptor.

The Lewis theory has the advantage of complementing the oxidation-reduction process paradigm. The movement of electrons from one atom to another occurs in oxidation-reduction reactions, resulting in a net change in the oxidation number of one or more atoms.

The Lewis theory also proposed that acids and bases share a pair of electrons when they react but that no oxidation numbers of any atoms change. Either one electron is transported from one atom to the next, or the atoms join forces to share a pair of electrons.

\({\text{Al}}{\left({{\text{OH}}} \right)_3} + 3{{\text{H}}^ + } \to {\text{A}}{{\text{l}}^{3 + }} + 3{{\text{H}}_2}{\text{O}}\) (Aluminium hydroxide is acting as a base)
\({\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}{\rm{ + O}}{{\rm{H}}^ – } \to {\rm{Al}}{\left( {{\rm{OH}}} \right)_4}^ – \) (Aluminium hydroxide is acting as an acid)
These are the reactions that are clearly visible: Aluminium hydroxide behaves as a base when it receives protons. It behaves as an acid when it takes electrons. This Lewis acid-base theory also explains why non-metal oxides like carbon dioxide dissolve in water and generate acids like carbonic acid \({{\text{H}}_2}{\text{C}}{{\text{O}}_3}.\)
\({\text{C}}{{\text{O}}_2}\left({\text{g}} \right) + {{\text{H}}_2}{\text{O}}\left({\text{l}} \right) \to {{\text{H}}_2}{\text{C}}{{\text{O}}_3}\left({{\text{aq}}} \right)\)

Limitations of Lewis Concept

1. The Lewis notion provided a broad concept that encompassed all coordination processes and molecules. This isn’t always the case.
2. The Lewis notion does not give us any information about the relative strength of acids and bases.
3. The Lewis notion is incompatible with the acid-base reaction theory.
4. The behaviour of protonic acids such as \({\text{HCl}}\) has not been covered in the Lewis idea.

Summary

1. Electrolytes are substances that produce ions when dissolved in water. Because they all produce ions when dissolved in water, they can be separated into acids, bases, and salts.
2. Arrhenius Concept: Acids are substances that produce \({{\text{H}}^ + }\) ions when dissolved in water, while bases are substances that ionise in water to form \({\text{O}}{{\text{H}}^ – }\) ions
3. Bronsted-Lowry ConceptAn acid is defined as any hydrogen-containing material (molecule, anion, or cation) that may donate a proton to another substance, while a base is defined as any substance (molecule, cation, or anion) that can absorb a proton from another substance, according to them.
4. Lewis Concept: Bases provide pairs of electrons to acids, whereas acids absorb pairs of electrons, according to Lewis’ theory of acid-base reactions. As a result, a Lewis acid can be described as an electron-pair acceptor.

FAQs on Acids, Bases and Salts

Q.1. What are electrolytes?
Ans: Electrolytes are substances that produce ions when dissolved in water. Because they all produce ions when dissolved in water, they can be separated into acids, bases, and salts. Because the positive and negative ions, known as cations and anions, are mobile in these solutions, they conduct electricity. When strong electrolytes are dissolved, they completely ionise, and no neutral molecules form in the solution. When weak electrolytes dissolve in water, a small fraction of their molecules ionises.

Q.2. What common salt is produced?
Ans: Apart from sodium chloride, other frequent salts are sodium nitrate, barium sulphate, and potassium chloride. The interaction between hydrochloric acid (acid) and sodium hydroxide produces sodium chloride, also known as common salt (base). Electrostatic forces hold a cluster of positively charged sodium ions and negatively charged chloride ions together in solid sodium chloride.

Q.3. What is Arrhenius concept of acids and bases?
Ans: Acids are substances that produce \({{\text{H}}^ + }\) ions when dissolved in water, while bases are substances that ionise in water to form \({\text{O}}{{\text{H}}^ – }\) ions, according to the Arrhenius idea.
\({\text{HA}} \to {{\text{H}}^ + } + {{\text{A}}^ – }\left({{\text{Acid}}}\right)\)
\({\text{BOH}} \to {{\text{B}}^ + } +{\text{O}}{{\text{H}}^ – }\left({{\text{Base}}} \right)\)
Acid-base reactions, according to Arrhenius, are characterised by acids dissociating in an aqueous solution to form hydrogen ions \(\left({{{\text{H}}^ + }} \right)\) and bases dissociating in an aqueous solution to form hydroxide \(\left({{\text{O}}{{\text{H}}^ – }} \right)\) ions.

Q.4. What is the Bronsted-Lowry concept of acids and bases?
Ans: In \(1923,\) Bronsted and Lowry developed a more comprehensive concept of acids and bases. An acid is defined as any hydrogen-containing material (molecule, anion, or cation) that may donate a proton to another substance, while a base is defined as any substance (molecule, cation, or anion) that can absorb a proton from another substance, according to them. Acids, on the other hand, are proton donors, while bases are proton acceptors.

Q.5. What are conjugate acid-base pairs?
Ans: Consider a reaction:
\({\text{Aci}}{{\text{d}}_1} + {\text{Bas}}{{\text{e}}_2} \to {\text{Aci}}{{\text{d}}_2} + {\text{Bas}}{{\text{e}}_1}\)
\({{\text{H}}_2}{\text{O}} + {\text{HCl}} \Leftrightarrow {{\text{H}}_3}{{\text{O}}^ + } + {\text{C}}{{\text{l}}^ – }\)
\({\text{HCl}}\) donates a proton to \({{\text{H}}_2}{\text{O}}\) in this process, making it an acid. Water, on the other hand, is a base because it accepts a proton from \({\text{HCl}}.\) The \({{\text{H}}_3}{{\text{O}}^ + }\) ions transfer a proton to the \({\text{C}}{{\text{l}}^ – }\) ion in the reverse process, which at equilibrium proceeds at the same rate as the forward reaction, making \({{\text{H}}_3}{{\text{O}}^ + }\) an acid. \({\text{C}}{{\text{l}}^ – }\) ion is a base because it receives a proton from the \({{\text{H}}_3}{{\text{O}}^ + }\) ion.

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