Preparation of Acids: All chemical compounds are divided into three categories based on different types of nature, i.e., acid, base and neutral substances. Acids are chemical substances that are sour in taste, sticky to touch and turn blue litmus solution or litmus paper to red. The word acid is derived from the Latin word acidus or acere, which means “sour,” as acids in water are sour in taste (e.g., vinegar or lemon juice).

In chemical laboratories, substances that convert blue litmus red are known as acids and substances that convert red litmus blue are known as bases. Compounds that release hydrogen ions in an aqueous solution are known as acids, for example, hydrochloric acid, sulphuric acid, acetic acid, and many more. Read through the article to find out more about strong acid examples, examples of strong bases, classification of amino acids and much more!

What is an Acid?

An acid is a chemical substance that accepts electrons, donates protons, or releases hydrogen \(\left( {{{\text{H}}^ + }} \right)\) ions in the aqueous solution. The \({\rm{pH}}\) of acid is less than \(7\). Examples of acids include sulphuric acid, hydrochloric acid, etc. Many natural substances contain acids that make them sour like lemon juice contains citric acid, tamarind contains tartaric acid, etc.

Acids have certain characteristic features that help to identify them. Some of them are:

1. They are sticky to the touch.
2. They are sour in taste.
3. Acids react with bases to form salts and catalyse certain chemical reactions.

Based on different concepts, acids can be defined as under:

1. According to the Arrhenius theory of acid, it is a chemical species that produces a hydrogen ion \(\left( {{{\text{H}}^ + }} \right)\) or proton in its solution.
2. The Bronsted-Lowry theory defines an acid as a proton donor.
3. Lewis acid is a compound or ionic species which can accept a lone pair of electrons to form a covalent bond.

Types of Acids

There are numerous ways to categorise acids.

Based on the strength, generally, acids are of two different types: strong acids and weak acids.

1. Strong Acid – An acid that completely dissociates into its \({{\text{H}}^ + }\) ions in water is known as a strong acid. These acids dissociate completely in water to form the same number of moles of hydrogen ions \(\left( {{{\text{H}}^ + }} \right)\) as the number of moles of acid added to water. This is the reason that the pH of a strong acid can be determined simply by knowing the concentration of the acid.
2. Weak Acid – An acid that incompletely dissociates in water is known as a weak acid. An aqueous solution of this type of acid includes both the weak acid and its conjugate base. Some examples of weak acids are acetic acid, carbonic acid, hydrofluoric acid, formic acid, etc.
3. Superacid – An acid that has an acidity greater than that of \(100\,\% \) pure sulphuric acid and has a Hammett acidity function of \(- \,12\) is known as a superacid. According to the latest definition, a superacid is a medium in which the proton’s chemical potential is higher than that in pure sulphuric acid. Some commercially available superacids are trifluoromethanesulfonic acid, also known as triflic acid, and fluorosulfuric acid; both superacids are around a thousand times stronger than sulphuric acid.

Based on the source, acids are of two types, organic and inorganic.

1. Organic Acids – Acids that are obtained from organic materials like plants and animals are known as organic acids. For example, lemon juice contains citric acid, tamarind contains tartaric acid, etc.
2. Inorganic Acids – Acids that are obtained from the minerals of the Earth, i.e., mineral acids are known as inorganic acids. For example: \({{\text{H}}_2}{\text{S}}{{\text{O}}_4}\), \({\text{HCl}}\), \({\text{HN}}{{\text{O}}_{\text{3}}}\), etc.

Properties of Acid

Below we have provided the physical and chemical properties of acids:

Physical Properties of Acid:

Different characteristic properties displayed by acids are as under:

1. The aqueous acidic solution is a good conductor of electricity as they dissociate into ions and are used as strong electrolytes.
2. Acids are corrosive in nature, so they should be handled with care; otherwise, they can corrode our skin too.
3. An acid turns blue litmus paper red, methyl orange to red, Bromothymol blue turns yellow in the presence of an acid. These indicators are used to detect the presence of acid in a solution.
4. The \({\rm{pH}}\) of an acidic solution is less than \(7\).
5. Acids are sour in taste

Chemical Properties of Acid:

An acid and a base react with each other to form a solution of salt and water, and this chemical reaction is known as a neutralisation reaction. In neutralization, an acid and a base in their aqueous state produce an aqueous solution of salt and water. If the salt is saturated or insoluble, then it can be precipitated out of the solution.

Uses of Acids

Different acids are used in various fields such as:

1. Dilute hydrochloric acid is used in various industries where heating applications are needed. It is used to remove deposits formed inside the boilers.
2. Hydrochloric acid is also used for household purposes like cleaning sinks and sanitary ware.
3. Sulphuric acid is a very important industrial chemical, and it is called the king of chemicals. It is used in car batteries.
4. It is used in the manufacture of drugs, paints, dyes, and to manufacture fertilizers.
5. Nitric acid is used by goldsmiths for cleaning gold and silver ornaments.
6. Fertilizers such as ammonium nitrate is produced from nitric acid.
7. Acetic acid is present in vinegar and is added as a food flavouring agent.
8. It is also used as a cleansing agent in substances meant for cleaning windows, floors, utensils, etc.
9. Acetic acid is used as food preservatives like in pickles, etc.

Industrial Preparation of Acid

There are several methods for preparing acids. Let’s discuss some of them:

1. Synthetic Method – Acids are mostly prepared by a direct combination of elements. For example, hydrogen chloride gas is prepared from hydrogen and chlorine under the action of an electric spark.
   \({{\text{H}}_{\text{2}}} + {\text{C}}{{\text{l}}_{\text{2}}}\xrightarrow{{{\text{electric}}\,{\text{spark}}}}2{\text{HCl}}\)
   Similarly, sulphuric acid is obtained from two elements; sulphur and, oxygen as follows:

2. By dissolving acidic oxides in water: Some oxides get dissolved in water to form acids. Such oxides are called acidic oxides. For example, sulphur trioxide \(\left( {{\rm{S}}{{\rm{O}}_3}} \right)\) gets dissolved in water to give sulphuric acid
\(\left( {{{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}} \right)\).
\({\rm{S}}{{\rm{O}}_3}\, + \,{{\rm{H}}_2}{\rm{O}}\, \to {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\).
Similarly, carbon dioxide dissolves in water to produce carbonic acid \(\left( {{{\rm{H}}_2}{\rm{C}}{{\rm{O}}_3}} \right)\).
\({\rm{C}}{{\rm{O}}_2}\, + \,{{\rm{H}}_2}{\rm{O}}\, \to \,{{\rm{H}}_2}{\rm{C}}{{\rm{O}}_3}\)

3. By the action of an acid on the salt of another acid: Acid having a higher boiling point can react with the salt of an acid with a lower boiling point to produce an acid. For example, Sodium chloride \(\left( {{\rm{NaCl}}} \right)\) is a salt of Hydrochloric acid \(\left( {{\rm{HCl}}} \right)\). The boiling point of \({\rm{HCI}}\) is lower than that of \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\). Thus, when \({\rm{NaCl}}\), which is the salt of \({\rm{HCl}}\), reacts with \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\), \({\rm{HCl}}\) is formed.
\({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\, + \,{\rm{NaCl}}\, \to \,{\rm{NaHS}}{{\rm{O}}_4}\, + \,{\rm{HCl}}\)

Summary

Acids are chemical substances that are sour in taste, sticky to touch and turn blue litmus solution or litmus paper to red. An acid is a chemical substance that accepts electrons, donates protons, or releases hydrogen \(\left( {{{\rm{H}}^{\rm{ + }}}} \right)\) ions in the aqueous solution. The pH of acid is less than \(7\). Examples of acids include sulphuric acid, hydrochloric acid, etc. Acids are defined based on different theories like Arrhenius according to the Arrhenius theory of acid, it is a chemical species that produces a proton or Hydrogen ion \(\left( {{{\rm{H}}^{\rm{ + }}}} \right)\) in its solution. The Bronsted-Lowry theory defines acids as proton donors. Lewis base is a compound or ionic species which can accept a lone pair of electrons to an acceptor compound. According to their degree of dissociation in aqueous solution and reactivity, acids are classified into strong acids, weak acids, and superacids. Acids are very useful for household as well as industrial purposes.

FAQs on Preparation of Bases

Q.1: What is the acid in chemistry?
Ans: An acid is a chemical substance that accepts electrons, donates protons, or releases hydrogen \(\left( {{{\rm{H}}^{\rm{ + }}}} \right)\) ions in the aqueous solution. The pH of acid is less than \(7\). Examples of acids include sulphuric acid, hydrochloric acid, etc. Many natural substances contain acids that make them sour like lemon juice contains citric acid, tamarind contains tartaric acid, etc.

Q.2: How are acids prepared?
Ans: Acids are prepared by different methods such as:
(i) Synthetic Method – Acids are mostly prepared by a direct combination of elements. For example, hydrogen chloride gas is prepared from hydrogen and chlorine under the action of an electric spark.
(ii) By dissolving acidic oxides in water: Some oxides get dissolved in water to form acids. Such oxides are called acidic oxides. For example, sulphur trioxide \(\left( {{\rm{S}}{{\rm{O}}_3}} \right)\) gets dissolved in water to give sulphuric acid \(\left( {{{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}} \right)\).
(iii) By the action of an acid on the salt of another acid: Acid having a higher boiling point can react with the salt of an acid with a lower boiling point to produce an acid. For example, Sodium chloride \(\left( {{\rm{NaCl}}} \right)\) is a salt of Hydrochloric acid \(\left( {{\rm{HCl}}} \right)\). The boiling point of \({\rm{HCl}}\) is lower than that of \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\). Thus, when \({\rm{NaCl}}\), which is the salt of \({\rm{HCl}}\) reacts with \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\), \({\rm{HCl}}\) is formed.

Q.3: What is the chemical formula of acetic acid?
Ans: In chemistry, acids are chemical substances that release hydrogen \(\left( {{{\rm{H}}^{\rm{ + }}}} \right)\) ions in the aqueous solution. The chemical formula of acetic acid or ethanoic acid is \({\rm{C}}{{\rm{H}}_3}{\rm{COOH}}\).

Q.4: How do you prepare carboxylic acid?
Ans: The carboxylic acid can be prepared by using Grignard reagents. Firstly, the Grignard reagent is allowed to react with crushed dry ice or solid \({\rm{C}}{{\rm{O}}_2}\). Salts of carboxylic acids are formed in this step, after that, these salts are acidified with mineral acids giving corresponding carboxylic acids.

Q.5: What are the 3 uses of acids?
Ans: The 3 uses of acids are:
(i)  Hydrochloric acid is also used for household purposes like cleaning sinks and sanitary ware.
(ii) It is used in the manufacture of drugs, paints, dyes, and to manufacture fertilizers.
(iii) Fertilizers such as ammonium nitrate is produced from nitric acid.

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