Salt is an ionic compound that contains a cation, other than a proton (H+) and an anion other than OH-. It is the main component of seawater and is an important substance for humans and animal life.
Salts are formed as one of the products in the neutralization reactions that occur between acids and bases.
For example; Acid + Base → Salt + Water
Salt can be a simple salt, acidic salt, double salt, basic salt, etc. These types depend on the partial or complete replacement of the hydrogen atoms of an acid molecule by a metal or a radical that acts like a metal. For example, see the below reaction;
HCl + NaOH → NaCl (salt) + H2O
HnO3 + KOH → KNO3 (Salt) + H2O
The commonly used salt in our daily life is sodium chloride. Its chemical formula is NaCl. Almost everyone knows about this salt because of its widespread use in cooking and food items and other products such as toothpaste, soaps, bleaches, plastic, etc. Salt is neutral in nature as its pH is 7 that makes it neither acidic nor basic.
Types of Salt
1. Acidic salt:
This type of salt is formed by partial neutralization of a diprotic or a polyprotic acid. In other words, it is formed by partial replacement of H ions present in an acid by a metal. So, an acidic salt has an ionisable H+ ion along with another cation. They are used in baking. Some examples of acidic salts are NaHSO4, NaHCO3 and KH2PO4.
2. Basic or Alkali Salt:
It is formed by the partial neutralization of a strong diacidic or triacidic base by a weak acid. It forms a basic solution when hydrolysed as the conjugate base of the weak acid is formed in the solution. For example, White lead (2PbCO3.Pb(OH)2)
3. Normal Salt:
As the name suggests, these salts are neutral, which are formed when acids and bases neutralize each other, which means all the hydrogen ions of acid are replaced by a metal present in the base. This is because they don’t contain any replaceable hydrogen or hydroxyl ions in their formula. For example, KNO3, NaCl and CuSO4, etc.
4. Double Salt:
They have more than one cation or anion. They are crystalline salts that are a mixture of two simple salts, but, they have their own crystal structure which is different from either salt. For example, bromlite, potassium sodium tartrate, aluminium sulfacetate, etc.
5. Mixed salt:
It is a type of salt that is formed from more than one base or acid. It is made of a fixed proportion of two salts that share a common cation or anion. For example, sodium potassium sulphate, bleaching powder, etc.
6. Complex salt:
It contains a complex neutral molecule. This molecule has a central metal ion which is surrounded by a number of neutral molecules or negative ions. For example, potassium ferrocyanide, potassium Argento-cyanide, etc.
Difference between Acidic and Basic Salt
A basic salt holds the conjugate base of a weak acid. So, acetate is a conjugate base of a weak acid, which is acetic acid. Therefore, sodium acetate is a basic salt.
Similarly, an acidic acid holds the conjugate acid of a weak base. For example, an ammonium ion is the conjugate acid of weak base ammonia. So, ammonium chloride is an acidic salt.
The conjugate base of a strong acid such as Cl– from HCl, and the conjugate acid from a strong base such as Na+ from NaOH produce neutral salts such as NaCl.
Some of the major differences between acidic salt and basic salt are given below;
|It has replaceable hydrogen ions.
|It contains replaceable hydroxyl ions.
|It gives hydrogen ions when ionizes or dissociates in water.
|It gives hydroxyl ions on ionization.
|It turns blue litmus red.
|It turns red litmus blue.
|It does not give any colour with phenolphthalein.
|It produces pink colour with phenolphthalein.
Hydrolysis of a Salt
It refers to the reaction of salt with water. It is the opposite of a neutralization reaction so, in the hydrolysis of salt, its constituent acid and base are formed as products. In other words, the salt dissociates completely or partially to form ions depending on the solubility of that salt.
Uses of Salts
There are various salts that are used in different industries and in various processes that are part of our daily life. Some of the commonly used salts that have lots of uses are described below;
Uses of Sodium chloride (common salt or table salt) I (NaCl)
- It is used in cooking not only for taste but also as an essential compound required by our body.
- It is used as a preservative in the food industry and in the preparation of pickles.
- It is used in the manufacturing of soaps, shampoo, toothpaste and glass production.
- It is used to melt ice and to prevent the accumulation of ice on roads, bridges, etc., during winter in cold countries.
- It is required as a raw material in the preparation of chemicals like baking soda, washing soda, etc.
- It helps prevent sodium loss in our body due to dehydration, and excessive sweating, etc.
Uses of Sodium hydroxide (alkali salt) I (NaOH)
- It is used as one of the main constituents in manufacturing soaps.
- It is used for cleaning as its solution is corrosive in nature so it can easily clean utensils, drains, ovens, tiles and other tools and surfaces. It can remove grease, grime, and oil very easily.
- It is needed to formulate different kinds of medicines in pharma companies.
- It is used in various reactions in laboratories.
- Its solution helps in removing harmful substances like dye, chemicals, etc., from fruits and vegetables.
- In the paper industry, caustic soda is used for making pulp and paper.
- In the aluminium industry, it is used to make various aluminium products.
Uses of Sodium carbonate (Na2CO3)
- It is used as a washing soda for washing clothes and is widely used in the production of soaps and detergents.
- It is required in the production of paper, caustic soda, glass, and the textile industry.
- It is required in the petroleum refining industry and fire extinguishers.
- It is required for the production of rayon polymers and for softening water.
- It is needed in the processing and tanning of animal hides.
- It is also found in toothpaste as a foaming agent.
- It is used in the brick industry and as a laboratory agent in laboratories.
Uses of Sodium bicarbonate (NaHCO3)
- It is used as baking soda for baking food items.
- It is also used in fire extinguishers.
- It acts as an antacid to treat acidity, indigestion and heartburn.
- It is also used in injection during severe health issues like renal failure, heart stroke, severe diabetes, etc.
- It is required in the production of cosmetics, personal hygiene products, etc.
- It has antibacterial properties so it helps clean teeth and mouth.
- It is used in pest control as it can kill insects like cockroaches and can control fungal growth.
- It helps prevent bad odour from armpits and can be used as a disinfectant.
Uses of Copper sulphate (CuSO4)
- It is used as a fungicide as it can kill various fungi.
- It helps in the testing of reducing sugars.
- It helps in the testing of blood samples while diagnosing diseases like anaemia.
- It is required in the dyeing of vegetables as a dye fixative.
- It is used in anti-fouling paints.
- It is also needed to add colour to cement, ceramics, glass and other metals.
- It is also a component of bookbinding glues to protect the papers from insects.
Uses of Calcium Hypochlorite Ca(ClO)2
- It is used to disinfect large water bodies to make their water safe for drinking.
- It is also used to sanitize the water of swimming pools.
- It is widely used as an oxidizing agent in organic chemistry.
- It produces chloroform in the haloform reactions.
- It is required for bleaching pulp, cotton, hemp, etc.
- In the kitchen, it is used to sanitize equipment and surfaces.
Properties of salts
- Salts are mostly transparent. However, some may exist as white powders.
- Salts of strong acids and bases are known as strong salts. They are generally odourless and non-volatile. Whereas, weak salts may have smells such as vinegar, ammonia, etc.
- Different salts may taste different such as lead diacetate has a sweet taste, sodium chloride is salty, magnesium sulphate is bitter, potassium bitartrate is sour, etc.
- Salts are insulators, however, salt solutions or molten salts can conduct electricity due to this reason they are considered electrolytes.
- They have high melting points. For example, sodium chloride melts at around 800 degrees centigrade. Some salts may exist in the liquid state at room temperature such as molten salts (mixtures of ionic liquids and salts).
Difference between acids, bases and salts in tabular form
|They produce hydrogen ions (H+) when dissolved in water.
|They produce hydroxyl ions (OH-) in the water solution.
|They do not produce these ions and form acidic or basic solutions.
|Their pH is less than 7.
|The pH value is more than 7.
|It is a neutral product of an acid and base reaction.
|It turns blue litmus paper to red.
|It turns red litmus paper to blue.
|It has no effect on the litmus paper.
|It remains colourless when phenolphthalein is added to it.
|Its solution turns pink when phenolphthalein is added to it.
|It shows no change in colour when phenolphthalein is added.
|Their chemical formula generally starts with H, e.g., HCl, H2SO4, etc.
|Their chemical formula has OH at the end, such as NaOH.
|Their chemical formula does not have a specific pattern.
|They have a sour taste, e.g., lemons, oranges, etc.
|They taste bitter.
|They have five different tastes which include salty, sweet, sour, bitter, and savoury.
|They produce a compound and hydrogen gas when they react with metals.
|They do not react with metals.
|More reactive metal displaces a less reactive metal from its salt solution.
|They give a stinging sensation when place on a wound.
|They are soapy in nature, so, slippery to touch.
|They mostly occur as a white powder.
|They can conduct electricity.
|They also conduct electricity.
|They generally do not conduct electricity.