We are surrounded by a variety of different materials with different properties. These materials consist mainly of compounds and elements. We find a variety of compounds in our daily activities. Some of them are savoury, some of them bitter, and some of them are salty. Lemon juice, for example, is sour, soap is bitter and seawater is salty.

Have you thought about why they have different tastes? Due to a number of compounds, such as acids, bases and salts, these substances have different tastes. More information on acids, bases and salts will be available in this article.

Acids

The word ‘acid’ comes from the Latin word acidus, which means sour. Everything that has a sour taste has an acid. Acids are chemicals with a sour taste. The acid solution’s pH is less than seven. Lemon fruit juice, tomatoes and vinegar, for instance, are all sour flavours. There must therefore be acid in each of these substances. Organic acids are referred to as the acids present in plant and animal materials. Mineral acids are known as the acids prepared from the earth’s minerals. Hydrogen ions are common in acids. An acid thus dissolves into water to produce the solution of hydrogen ions \(\left( {{{\rm{H}}^ + }} \right)\)

Some of the naturally occurring substances that contain acids are given in Table.

Substance	Acid present
Orange, lemon	Citric acid, ascorbic acid
Apple	Malic acid
Tamarind, grape	Tartaric acid
Vinegar	Acetic acid
Curd	Lactic acid
Tomato	Citric acid and malic acid
Gastric juice	Hydrochloric acid
Tea	Tannic acid
Red ants	Formic acid

Study Chemical Properties of Acids and Bases

Types of Acids

Acid can be classified into two types. They are;

1.Strong acids: An acid that is completely ionized in water and thus produces a large amount of hydrogen ions is called a strong acid. All mineral acids are strong acids except carbonic acid because it is a weak acid. Strong acids are very dangerous to drink. Hydrochloric acid, sulphuric acid and nitric acids are strong acids.
2. Weak acids: An acid that is partially ionized in water and thus produces a small amount of hydrogen ions is called a weak acid. Organic acids are weak acids. The dilute solutions of weak acids are perfectly safe to consume. Because organic acids like acetic acid, citric acid, and tartaric acid are weak, they are used as food ingredients. Acetic acid (in the form of vinegar) is used in the production of pickles and tomato ketchup, tartaric acid in baking powder, and carbonic acid in fizzy soft drinks and soda water.

Concentrated and Dilute acids

Concentrated acid is the one that contains the minimum amount of water. Whereas dilute acid is one that contains much more water.

Diluting acids

A dilute acid is obtained by mixing the concentrated acid with water. The dilution of a concentrated acid should always be done by adding concentrated acid to water gradually with stirring and not by adding water to concentrated acid. This is because

1. When a concentrated acid is mixed with water to make a dilute acid, the heat is gradually released and easily absorbed by a large amount of water.
2. If water is added to concentrated acid to dilute it, a large amount of heat is released all at once. This heat causes some of the water to explode into steam, which can splash the acid on our faces or clothes, causing acid burns. Excessive heating may cause the glass container to shatter.

Properties of Acids

The important properties of acids are as follows:

1. Acids have a sour taste.
2. Acids turn blue litmus to red.
3. Acids solution conducts electricity due to the presence of hydrogen ions.
4. Acids have a corrosive nature.
5. Acids react with metals to form hydrogen gas.

\({\rm{Metal}} + {\rm{Acid}} \to {\rm{Salt}} + {\rm{Hydrogen}}\,{\rm{gas}}\)

For example, when dilute sulphuric acid reacts with zinc metal, then zinc sulphate is formed with the liberation of hydrogen gas.

\(\mathop {{\rm{Zn}}}\limits_{{\rm{Zinc}}} \, + \,\mathop {{{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}}\limits_{{\rm{Sulphuric}}\,{\rm{acid}}}  \to \mathop {{\rm{ZnS}}{{\rm{O}}_4}}\limits_{{\rm{Zinc}}\,\,{\rm{sulphate}}}  + \mathop {{{\rm{H}}_2}}\limits_{{\rm{Hydrogen}}\,{\rm{gas}}} \)

6. Strong acids react with metal carbonate and metal hydrogen carbonate and form carbon dioxide gas.

\({\rm{Metal}}\,{\rm{carbonate}}\, + {\rm{Acid}}\, \to {\rm{Salt}}\, + {\rm{Water}} + {\rm{Carbonate}}\,{\rm{dioxide}}\)

\({\rm{Metal}}\,{\rm{Hydrogen}}\,\,{\rm{carbonate}} + {\rm{Acid}}\, \to {\rm{Salt}}\, + {\rm{Water}} + {\rm{Carbonate}}\,{\rm{dioxide}}\)

For example,
I. When dilute hydrochloric acid reacts with sodium carbonate, then sodium chloride, water and carbon dioxide gas are formed:

\(\mathop {{\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}}\limits_{{\rm{Sodium}}\,\,{\rm{carbonate}}} \, + \,\mathop {2{\rm{HCl}}}\limits_{{\rm{Hydrochloric}}\,{\rm{acid}}}  \to \mathop {2{\rm{NaCl}}}\limits_{{\rm{Sodium}}\,\,{\rm{chloride}}}  + \mathop {{\rm{C}}{{\rm{O}}_2}}\limits_{{\rm{Carbon}}\,\,{\rm{dioxide}}}  + \mathop {{{\rm{H}}_2}{\rm{O}}}\limits_{{\rm{Water}}} \)

II. When dilute hydrochloric acid reacts with sodium bicarbonate, then sodium chloride, carbon dioxide and water are formed.

\(\mathop {{\rm{NaHC}}{{\rm{O}}_3}}\limits_{{\rm{Sodium}}\,\,{\rm{carbonate}}} \, + \,\mathop {{\rm{HCl}}}\limits_{{\rm{Hydrochloric}}\,\,{\rm{acid}}}  \to \mathop {{\rm{NaCl}}}\limits_{{\rm{Sodium}}\,\,{\rm{chloride}}}  + \mathop {{\rm{C}}{{\rm{O}}_2}}\limits_{{\rm{Carbon}}\,\,{\rm{dioxide}}}  + \mathop {{{\rm{H}}_2}{\rm{O}}}\limits_{{\rm{Water}}} \)

7. Acids react with a base to form salt and water. The reaction between an acid and a base to form salt is known as a neutralisation reaction.

\({\rm{Acid}}\, + \,{\rm{Base}}\, \to \,{\rm{Salt}}\, + {\rm{Water}}\)

For example, When hydrochloric acid reacts with sodium hydroxide solution, a neutralization reaction takes place and forms sodium chloride and water.

8. Acids react with metal oxides and form salt and water.

For example, when hydrochloric acid reacts with copper (II) oxide to form copper (II) chloride and water.

\(\mathop {{\rm{CuO}}}\limits_{{\rm{copper}}{\kern 1pt} ({\rm{II}})\,{\rm{oxide}}} {\mkern 1mu}  + {\mkern 1mu} \mathop {2{\rm{HCl}}}\limits_{{\rm{Hydrochloric}}{\kern 1pt} {\kern 1pt} {\rm{acid}}} {\mkern 1mu}  \to \mathop {{\rm{CuC}}{{\rm{l}}_2}}\limits_{{\rm{Copper}}{\kern 1pt} ({\rm{II}}){\kern 1pt} {\kern 1pt} {\rm{chloride}}}  + {\mkern 1mu} \mathop {{{\rm{H}}_2}{\rm{O}}}\limits_{{\rm{Wate}}r} \)

Uses of Mineral Acids in Industry

1. Sulphuric acid is used in the manufacture of fertilisers, paints, chemicals, plastics, detergents, etc.
2. Nitric acid is used in the manufacture of fertilisers, explosives, dyes and plastics.
3. Hydrochloric acid is used to remove oxide film from steel objects as well as scale deposits from within boilers. It’s also used in dyestuffs, textiles, food, and leather.

Bases

Bases are those chemical substances that have a bitter taste. Bases are the chemical opposite to acids. A base is a substance that can neutralize an acid. All the bases change the colour of red litmus to blue. The pH of the basic solution is above \(7.\) Some common examples of bases are sodium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium hydroxide, etc.

A base that is soluble in water is called alkali. Sodium hydroxide, potassium hydroxide, calcium hydroxide are some examples of alkalis. Bases have hydroxide ions in common. Thus, a base is a substance that dissolves in water to produce hydroxide ions \(({\rm{O}}{{\rm{H}}^ – })\) in the solution.

Types of Bases

Bases are classified into two types. They are;

1. Strong Bases: A base that completely ionises in water and thus produces a large amount of hydroxide ions \(({\rm{O}}{{\rm{H}}^ – })\) is called a strong base (or a strong alkali). Sodium hydroxide \(({\rm{NaOH}})\)

2. Weak Bases: A base that is partially ionised in water and thus produces a small amount of hydroxide ions \(\left( {{\rm{O}}{{\rm{H}}^ – }\,{\rm{ions}}} \right)\) is called a weak base. Ammonium hydroxide, calcium hydroxide and magnesium hydroxide are weak bases.

Properties of Bases

The important properties of Bases are as follows:

1. Bases have a bitter taste
2. Bases feel soapy to touch
3. Bases turn red litmus to blue
4. Bases conduct electricity due to the presence of hydroxide ions.
5. Bases react with some metals to form salt and hydrogen gas. For instance, sodium and hydrogen gas are formed if the solution for sodium hydroxide is heated by zinc.
6. Bases react to salt and water with acids. This reaction is called a reaction of neutralisation. For instance, sodium chloride and water are formed when hydrochloric acid reacts. This is an example of a reaction of neutralisation.
   \({\rm{NaOH}} + {\rm{HCl}}\, \to \,{\rm{NaCl + }}{{\rm{H}}_2}{\rm{O}}\)
7. Bases react with non-metal oxides to form salt and water.
   \({\rm{Non}}\,{\rm{ – }}\,{\rm{metal}}\,{\rm{oxide}}\,{\rm{ + }}\,{\rm{Base}}\, \to \,{\rm{Salt}}\,{\rm{ + }}\,{\rm{Water}}\)
   For example, calcium hydroxide reacts with carbon dioxide and produces calcium carbonate and water.

\(\mathop {{\rm{Ca}}{{({\rm{OH}})}_2}}\limits_{{\rm{Calcium}}{\kern 1pt} {\rm{hydroxide}}} {\mkern 1mu}  + {\mkern 1mu} \mathop {{\rm{C}}{{\rm{O}}_2}}\limits_{{\rm{Carbon}}{\kern 1pt} {\rm{dioxi}}{\kern 1pt} {\rm{de}}} {\mkern 1mu}  \to \mathop {{\rm{CaC}}{{\rm{O}}_3}}\limits_{{\rm{Calcium}}{\kern 1pt} {\kern 1pt} {\kern 1pt} {\rm{carbonate}}}  + {\mkern 1mu} \mathop {{{\rm{H}}_2}{\rm{O}}}\limits_{{\rm{Wate}}r} \)

Uses of Bases

The following are some of the most important applications of bases:

1. Sodium hydroxide is used in the production of soap, paper, and rayon, a synthetic fibre.
2. Calcium hydroxide (also known as slaked lime) is used in the production of bleaching powder.
3. Magnesium hydroxide is used as an antacid to neutralise excess stomach acid and cure indigestion.
4. Sodium carbonate is used to soften hard water and as a washing soda.
5. Sodium hydrogen carbonate is used in baking soda, baking powders, as an antacid to treat indigestion, and in soda-acid fire extinguishers.

Salts

Salt is an acid-formed compound that substitutes for acid hydrogen with a metal. When acids react with the foundations, salts are formed. The \({\rm{pH}}\) of the salt solution is generally \({\rm{7}}\). The most well-known salt is sodium chloride \(\left( {{\rm{NaCl}}} \right)\) also known as common salt. Other salts are Calcium chloride, magnesium chloride, magnesium chloride, zinc chloride, aluminium sulphate, zinc carbonate, sodium acetate, etc.

Properties of Salts

1. Salts are mostly solids.
2. Salts are ionic compounds. Hence they have high melting points and boiling points.
3. Salts are usually soluble in water
4. Just like acids and bases, the salt solution also conducts electricity due to the presence of ions in them.

The \({\rm{pH}}\) of the salt solution: The aqueous solutions of many salts are neutral (having a \({\rm{pH}}\) of \(7\)), but when dissolved in water, some salts produce acidic or basic solutions. The acidic nature and basic nature of some salt solutions can be explained based on the hydrolysis of salts.

Types of Salts

Salts are of three types. They are as follows:

1. The salts of strong acids and strong bases give a neutral solution.
2. The salts of strong acids and weak bases give acidic solutions.
3. The salts of weak acids and strong bases give basic solutions.

Uses of Salts

1. Common salt is used as a raw material for making a large number of useful chemicals in the industry such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, hydrochloric acid, chlorine, hydrogen and sodium metal.
2. Common salt is used in cooking food.
3. Common salt is used as a preservative in pickles, and in currying meat and fish.
4. Common salt is used in the manufacture of soap.
5. Washing soda is a transparent crystalline solid.
6. Sodium carbonate is used in the manufacture of sodium compounds such as borax.
7. Sodium hydrogen carbonate is used as an antacid in medicine to remove the acidity of the stomach.

Summary

Acids are substances that have a sour taste. Bases are substances that have a bitter taste, Salts are substances that have a salty taste. Acids turn blue litmus paper to red, Bases turn red litmus paper to blue. Most of the salts do not turn the colour of litmus paper. Acids, bases and salts have many applications in day to day life and in industry, agriculture, etc.

FAQs on Acids, Bases and Salts

Q.1.What are the examples of acid, base and salt?
Ans: Examples of acids are citric acid, lactic acid, hydrochloric acid, sulphuric acid.
Examples of Bases are sodium hydroxide, calcium hydroxide, magnesium hydroxide.
Examples of salts are sodium chloride, magnesium sulphate, calcium chloride.

Q.2. What are the properties of acid, base and salt?
Ans: Properties of acids, bases and salts are as follows:

Substances	Acids	Bases	Salts
Properties	These have a sour taste and turn blue limits Paper to blue	These have a bitter taste and red litmus paper to blue	These are solid substances with a salty taste these have a high boiling point and melting point

Q.3. What are the characteristics of acid, base and salt?
Ans: Characteristics of acids, bases and salts are as follows:

Characteristics	Acids	Bases	Salts
1. Taste 2. Litmus Paper test 3. Reaction with	1. Acids Have a sour taste 2. Acid turns blue litmus to red 3. Acids react	1. Bases Have a bitter taste and are soapy too much 2. Bases turn red litmus to red 3. Some of the bases react with metals and form hydrogen gas.	1. Salts are mostly solids and have a salty taste. 2. Salts are ionic compounds Hence they have high melting pointing and boiling points 3. Salts are usually soluble in water

Q.4. What are the uses of acid, base and salt?
Ans: Uses of acids and bases and salts are as follows:

Substances	Acids	Bases	Salts
Uses	1. Sulphuric acid is used in table manufacture of fertilisers, paints, chemicals, plastics, detergents, etc.	1. Sodium hydroxide is used in the production of soap, paper, and rayon, a synthetic fibre.	1. Common salt is used as a preservative in pickles and in currying meat and fish.
	2. Nitric acid is used in the manufacture of fertilisers, explosives, dyes and plastics.	2. Calcium hydroxide (also known as slaked lime) is used in the production of bleaching powder.	2. Common salt is used in the manufacture of soap.
	3. Hydrochloric acid is used to remove oxide film from steel objects as well as ‘scale’ deposits from within boilers. It’s also used in dyestuffs, textiles, food, and leather.	3. Magnesium hydroxide is used as an antacid to neutralise excess stomach acid and cure indigestion.	3. Washing soda is a transparent crystalline solid made of sodium carbonate.

Q.5. What do you mean by acid, base and salt?
Ans: Acids are those chemical substances that have a sour taste.
Bases are those chemical substances that have a bitter taste.
Salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.

Q.6. What is the difference between acids, bases and salt?
Ans: The main difference between acids, bases and salts are as follows:

Acids	Bases	Salts
Acids turn blue litmus to red.	Bases turn red litmus to blue.	No effect on litmus paper.
Acids have a \({\rm{pH}}\) value less than \({\rm{7}}\).	Bases have a \({\rm{pH}}\) value more than \({\rm{7}}\)	Salts generally have \({\rm{pH}}\) Value \({\rm{7}}\)
Acid is a substance that dissolves in water to produce hydrogen ions \({\rm{(}}{{\rm{H}}^ + })\) in the solution.	The base is a substance that dissolves in water to produce hydroxide ions \({\rm{(O}}{{\rm{H}}^ – })\)	Salt is a compound formed by the partial or total replacement of the ionisable hydrogen atoms of an acid by a metallic ion or an electropositive ion.