The discovery of salt played a crucial role in developing civilizations in the past. It was very valuable to the ancient Greek people, the Roman people, and other people around the globe. The word “salary” is derived from a Latin word for salt because the workers in Rome were often paid in salt, which had its worth equal to the worth of gold.

Today, salt is an indispensable part of our lives. The common freshly mined salt and even sea salt contain minute quantities of certain elements that are essential for animal and plant health. Salt allows people to keep their food fresh for much longer and also allows the transportation of food over long distances. 

What is salt in chemistry?

The chemical name of common salt is sodium chloride (NaCl), which represents an equal weightage of chlorine and sodium. The word salt has multiple meanings in chemistry. When you ask somebody to pass the salt at dinner, you refer to ‘table salt’, which is sodium chloride, abbreviated as NaCl. Sodium chloride is an example of salt in chemistry. Salt is an ionic substance formed by combining an acid with a base or naturally as a mineral. In other words, salt is formed due to a neutralisation process.  Salt crystals have various characteristics such as white in colour, transparency in appearance, and roughly cubic.

Properties of Salt

• Colour: colourless, transparent, or white.

• Taste: different salts can depict all the five basic tastes, sour, sweet, salty, bitter, and even a hint of savoury or umami.

• Odour: Odourless

• Melting Point/Boiling Point: The melting point of sodium chloride is 800 degrees Celsius or 1,072 degrees Kelvin. The boiling point of sodium chloride or salt is 1,737 degrees Kelvin or 1,464 degrees Celsius. (roughly)

Structure of Salt

Only those ions joined with the help of lines touch one another. 6 ions of chlorine touch the sodium ion that is located in the centre. Sodium chloride is 6:6 co-ordinated.

Solubility of salts

Types of salts

There are different types of salts, namely acidic salt, basic salt, neutral salt, and double salt.

Acidic Salt-

A salt that is formed as a result of the reaction between a weak base and a strong acid is called an ‘Acidic Salt’.

For Example- NH4Cl, CuSO4

Basic Salt-

A salt that is formed as a result of the reaction between a weak acid and a strong base is called a ‘Basic Salt’.

For Example- Na2S, CH3COONa, etc.

Neutral Salt-

A salt that is formed as a result of the reaction between a strong acid and a strong base is called a ‘Neutral Salt’.

For Example- NaCl, KNO3, etc.

Double Salt–

A salt formed with the equimolar proportions of the two simple salts when they are crystallised at a slow pace and form a mixture of their saturated salt solution.

For Example-  K2SO4.Al2(SO4)3. 24H2O (Potash Alum).

Mixed Salt-

A salt that contains more than one cation or anion atom different from H+ ions is called Mixed Salt. 

For Example- CaOCl2

Experiment for the identification of a salt (acidic, neutral, or basic)

Aim: To identify the salts (acidic, basic, or neutral) using a litmus paper indicator.

Material: Salt solution, detergent solution, soap solution, orange juice, four glass beakers, water, dropper, dropper plate, litmus paper.

Procedure:

1. Cut the litmus paper into 1 cm each.
2. Pour the salt, detergent, orange, and soap solutions into four glass beakers.
3. Then, using a dropper, put some drops of the solutions into the dropper plate.
4. Insert the litmus paper red and blue into the solutions and observe.

Observation:

1. The blue litmus paper breaks because the orange juice solution is acidic 
2. In the basic solutions, soap and detergent, the colour of the red litmus paper becomes lighter.
3. In the neutral solutions, salt does not change the colour of the litmus paper.

Conclusion of the experiment:

The acidic solution breaks the blue litmus paper, and basic solutions make the litmus paper lighter.

Whereas in neutral solutions, the litmus does not change any colour.

Conclusion

Salt is a solid chemical compound that occurs naturally in nature in its pure form. They are formed due to a neutralisation reaction between acids and bases. Salt is classified into different types acidic, basic, normal, and double. Acidic salt is formed when a strong acid reacts with a weak base. Basic salt is formed when a strong base reacts with a weak acid, and neutral salt is formed when a strong acid and base react.

Salt is an integral part of our life as it is used to season food.

The sole motto of this module is to make the student understand the different types of salts, mainly acidic, basic, normal, and double salt, in Chemistry.