-> It is a substance which contain positive and negative ions or radicals and ionize completely in
aq. solution.
e.g. NaCl, Na2SO4, Na3PO4, etc.
-> Salts are electrically neutral. There are number of salts but sodium chloride is the most common among them.
-> Sodium chloride is also known as table salt or common salt.
It is used to enhance the taste of food.
* Family of salts- If two salts have same positive (basic radicals) and negative radicals (acidic radicals) then they are called to be of same family and known as family of salts.
e.g.
i) Sodium chloride (NaCl) and Calcium chloride (CaCl2) belongs to chloride family.
ii) Calcium chloride (CaCl2) and Calcium sulphate (CaSO4) belongs to calcium family.
iii) Zinc chloride (ZnCl2) and Zinc sulphate (ZnSO4) belongs to the zinc family.
Types of salts
* Normal salts- Those salts which produced between the reaction of a strong acid and a strong base are called normal salts.
The pH value of such salts is equal to 7 i.e. neutral.
e.g. Sodium chloride, Sodium sulphate. Potassium chloride, etc.
-> Sodium Sulphate (Na2SO4)- It is formed after the reaction between sodium hydroxide (a strong base) and sulphuric acid (a strong acid).
* Acidic salts- The salts which produce an acid solution after being dissolved in a solvent is called acidic salt.
Generally,
It is formed after the reaction between a strong acid and weak base are called Acidic salts. The pH value of acidic salt is lower than 7.
For e.g. Ammonium sulphate, Ammonium chloride, etc.
* Ammonium chloride (NH4Cl)- It is formed after reaction between hydrochloric acid (a strong acid) and ammonium hydroxide (a weak base).
NH4OH(aq) + HCl(aq) -----> NH4Cl(aq) + H2O(l)
* Ammonium Sulphate [(NH4)2SO4]- It is formed after reaction between sulphuric acid (a strong acid) and ammonium hydroxide (a weak base).
NH4OH(aq) + H2SO4(aq) -----> [(NH4)2SO4](aq) + H2O(l)
Note:- We can also convert acidic salts into normal salts.
For e.g.
-> Sodium Phosphate (Na3PO4)- It is formed after the reaction between excess sodium hydroxide (a strong base) and phosphoric acid (a weak acid).
* Basic salts- The salts which produce a basic solution after being dissolved in a solvent is called basic salt.
Generally, It is formed after the reaction between a weak acid and strong base. The pH value of acidic salt is more than 7.
For e.g. Sodium carbonate, Sodium acetate, etc.
-> Sodium carbonate (Na2CO3)- It is formed after the reaction between sodium hydroxide (a strong base) and carbonic acid (a weak acid).
NaOH(aq) + H2CO3(aq) ----> NH4Cl(aq) + H2O(l)
-> Sodium acetate (CH3COONa)- It is formed after the
reaction between a strong base, sodium hydroxide
(a strong base) and acetic acid, (a weak acid).
NaOH(aq) + CH3COOH(aq) ---> CH3COONa(aq) + H2O(l)
Note:- We can also convert basic salts into normal salts.
For e.g.
-> Calcium chloride (CaCl2)- It is formed after the reaction between calcium hydroxide (a weak base) and excess hydrochloric acid (a strong acid).
Characteristics of salt
* Most of the salts are crystalline solid.
* Salts may be transparent or opaque.
* Most of the salts are soluble in water.
* Solution of the salts conducts electricity in their molten state also.
* The salt may be salty, sour, sweet, bitter and umami (savoury).
* Neutral salts are odourless.
* Salts can be colourless or coloured.
Uses of normal salts
* It is used as a raw material for making useful chemical in industries.
* It is used in storing food items like pickles.
* It is used in manufacture of soap.
* It is used in melting of ice of the road.
* It is used to improve the taste of food.
Hydrated salt
-> Those salts in which water molecules are attached to its crystal are called hydrated salts.
* In these salts, a fixed number of water molecules gets attached to each molecules of the salt.
e.g. CuSO4.5H2O, FeSO4.7H2O, Na2SO4.10H2O, etc.
* Those salts which do not possess water of crystallization are called anhydrous salts.
e.g. CuSO4, FeSO4, Na2SO4, etc.
Note- All hydrated salt solution water of crystallization on heating and become anhydrous salts.
Sodium Hydroxide
-> Sodium hydroxide is also known as caustic soda. When electricity is passed through and aq. solution of sodium chloride then it decomposes and formed sodium hydroxide as the main product along with the chlorine and hydrogen gas as the side products.
This solution is called ‘brine solution’ and this
whole process is called chlor-alkali process because
of the product so formed. Chlor for chlorine and alkali for sodium hydroxide.
Note:- Chlorine is obtained at anode (+ve) and hydrogen gas is obtained at
cathode (-ve).
Uses of NaOH
* Used for making soaps and detergents.
* Used for making artificial textile fibres.
* Used in the manufacture of paper.
* Used for purifying bauxite ore.
* Used in degreasing metals, while refining and making dyes and bleaches.
Uses of H2
* Hydrogen gas is used as fuel, making of ammonia for fertilizer, etc.
Uses of Cl2
* Chlorine gas is used in water treatment, manufacturer of PVC, disinfectants, CFC, pesticides.
* It is also used in the manufacturing of bleaching powder and hydrochloric acid.
Bleaching powder
-> Bleaching powder is produced by the action of chlorine on dry slaked lime. It is also known as chloride of lime. It is a solid and yellowish-white in colour. It can be easily identified by the strong smell of chlorine.
-> Aqueous solution of bleaching powder is basic in nature. The term bleach means removal of colour. It is often used as bleaching agent because of presence of chlorine.
The chemical name of bleaching powder is calcium oxychloride or calcium hypochlorite.
Uses of Bleaching powder
* It is used as disinfectant to clean water, weed killers, etc.
* It is used for bleaching of cotton in textile industry,
bleaching of wood pulp in paper industry.
* It is used as oxidizing agent in many industries, such as textiles industry, paper industry, etc.
* It is used to make chloroform (CHCl3).
Note:- Wood pulp is a type of fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops, waste paper, etc.
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