02 Acid, bases and salt

  • Salt is abundantly present in sea water. It is the main mineral constituent of sea water and is essential for animal life.
  • A salt is an ionic compound formed from an acid by the replacement of the hydrogen in the acid by a metal. A cation other than H+and an anion other than OH are present.
  • Salt is obtained along with water in the neutralization reaction between acids and bases.
  • Salts are formed when acids react with bases.
  • Acid + Base  Salt + water
  • The salts of hydrochloric acid are called chlorides.
  • The salts of sulphuric acid are called sulphates.
  • The salts of Nitric acid are called Nitrates.
  • The salts of Carbonic acid are called Carbonates.
  • The salts of Acetic acid are called acetates.

Some Important Salts and their Formulae

Salt Formula
Sodium Chloride NaCl
Calcium chloride CaCl2
Sodium sulphate

Na2SO4

Zinc sulphate ZnSO4
Copper sulphate CuSO4
Sodium nitrate NaNO3
Sodium carbonate Na2CO3
Calcium carbonate CaCO3

THE pH OF SALT SOLUTIONS

  • Though the aqueous solutions of many salts are neutral so it has having a pH of 7, but some salts produce acidic or basic solutions (alkaline solution) when dissolved in water.
    • The salt of strong acids and strong bases give neutral solution . Sodium chloride salt (NaCl) is formed from a strong acid hydrochloric acid (HCl), and a strong base sodium hydroxide (NaOH).
    • The salts of strong acids and weak bases give acidic solution, so it has pH less than 7. Ammonium chloride (NH4Cl) is the salt of a strong acid hydrochloric acid (HCl), and a weak base ammonium hydroxide (NH4OH).
    • The salts of weak acids and strong bases give basic solutions (or alkaline solutions) (having pH more than 7). Sodium carbonate (Na2CO3) is the salt of a weak acid carbonic acid (H2CO3) and a strong base sodium hydroxide (NaOH).

HYDROLYSIS OF A SALT

  • The reaction of salt with water is known as hydrolysis of salt. The constituent acid and base are formed as products. Salt dissociates to form ions, completely or partially depending upon the solubility product of that salt. It is the reverse of a neutralization reaction.

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