Class 10 Chemistry



Acid Base and Salt

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 salts conducts electricity. Salts conduct 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

Salt

Salts are the ionic compounds which are produced after the neutralization reaction between acid and base. 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. Sodium chloride is used to enhance the taste of food.

Family of Salt:

Salts having common acidic or basic radicals are said to belong to same family.

Example: Sodium chloride (NaCl) and Calcium chloride (CaCl2) belong to chloride family.

Calcium chloride (CaCl2) and calcium sulphate (CaSO4) belong to calcium family.

Zinc chloride (ZnCl2) and Zinc sulphate (ZnSO4) belong to zinc family.

Acidic, Basic and Neutral Salts

Neutral Salt: Salts produced because of reaction between strong acid and strong base are neutral in nature. The pH of value of such salts is equal to 7, i.e. neutral. Example; Sodium chloride, sodium sulphate, potassium chloride, etc.

Sodium chloride (NaCl) is formed after the reaction between hydrochloric acid (a strong acid) and sodium hydroxide (a strong base).

NaOH + HCl ⇨ NaCl + H2O

Sodium sulphate (Na2SO4): It is formed after the reaction between sodium hydroxide (a strong base) and sulphuric acid (a strong acid).

2NaOH + H2SO4 ⇨ Na2SO4 + 2H2O

Potassium chloride (KCl): It is formed after the reaction between potassium hydroxide (a strong base) and hydrochloric acid (a strong acid).

KOH + HCl ⇨ KCl + H2O


Acidic salt:

Salts which are formed after the reaction between a strong acid and weak base are called acidic salt. The pH value of acidic salt is lower than 7. Example: ammonium sulphate, ammonium chloride, etc.

Ammonium chloride is formed after reaction between hydrochloric acid (a strong acid) and ammonium hydroxide (a weak base).

NH4OH + HCl ⇨ NH4Cl + H2O

Ammonium sulphate is formed after reaction between ammonium hydroxide (weak base) and sulphuric acid (a strong acid).

2NH4OH + H2SO4 ⇨ (NH4 )2SO4 + 2H2O

Basic Salt: Salts which are formed after the reaction between weak acid and strong base are called basic salt. For example; sodium carbonate, sodium acetate, etc.

Sodium carbonate is formed after the reaction between sodium hydroxide (a strong base) and carbonic acid (a weak base).

H2CO3 + 2NaOH ⇨ Na2CO3 + 2H2O

Sodium acetate is formed after the reaction between a strong base, sodium hydroxide and a weak acid, acetic acid.

CH3COOH + NaOH ⇨ CH3COONa + H2O


Cause of formation of acidic, basic and neutral salt:

When a strong acid reacts with a weak base, the base is unable to fully neutralize the acid. Due to this an acidic salt is formed in this case.

When a strong base reacts with a weak acid, the acid is unable to fully neutralize the base. Due to this a basic salt is formed in this case.

When equally strong acid and base react they fully neutralize each other. Due to this a neutral salt is formed in this case.

pH value of salt:

  • Neutral salt: The pH value of a neutral salt is almost equal to 7.
  • Acidic salt: The pH value of an acidic salt is less than 7.
  • Basic salt: The pH value of a basic salt is more than 7.

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Acid

Base

Common properties

Strength

Common Salt

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