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| Classification of Salts |
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| Salts can be classified into the following types: |
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| a) Normal salt |
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| A salt that does not contain any replaceable hydrogen ions is a normal salt. It is obtained by replacing all the hydrogen ions of an acid by metal ions or ammonium ions. Examples: NaCl, Na2SO4, Na3PO4, NH4Cl, K2CO3, CuSO4 etc. |
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| b) Bisalts or Acid salts |
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| A bisalt, or an acid salt contains replaceable hydrogen ions in association with the acidic radicals. It is obtained by the incomplete replacement of hydrogen ions by metal ions or ammonium ions. |
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| Examples: NaHCO3, NaH2PO4 and Na2HPO4. |
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| Since such salts also contain hydrogen ion, the term 'bi' or acid can be substituted by hydrogen, e.g. sodium bicarbonate or sodium acid carbonate is also called sodium hydrogen carbonate. |
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| When bisalts or acid salts dissociate in water, they yield hydrogen or hydronium ions. |
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| Since an acid salt liberates hydrogen or hydronium ions, it exhibits some acidic properties. Hence it behaves like an acid. |
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| i) An acid salt reacts with bases to form salt and water only. |
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| iii) They react with carbonates to yield carbon dioxide. |
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| Some Common Acid Salts |
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| NaHCO3, NaHSO3, NaHSO4, Na2HPO4, Ca(HCO3)2, Ca(HSO4)2, KHCO3, KHSO3, KHSO4, NaH2PO4 and Mg(HCO3)2 |
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| c) Basic Salts |
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| A basic salt is formed by the action of an acid with higher proportion of the base, than is necessary for the formation of a normal salt. |
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| Example: |
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| Basic copper carbonate CuCO3.Cu(OH)2 |
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| Basic lead carbonate (white lead) PbCO3.Pb(OH)2 |
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| A basic salt may also be formed by the partial replacement of the hydroxyl groups of a diacidic or triacidic base, by an acid radical. |
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| Basic salts are usually insoluble in water. |
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| d) Double Salts |
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| Such salts are formed by the intimate association of two simple salts, when crystallized from a solution of a mixture of the two. |
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| e) Mixed Salts |
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| Salts that contain more than one acid radical or basic radical are called as mixed salts. |
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| f) Binary Salts |
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| Salts that contain atoms of two elements only are termed as binary salts. |
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| g) Ternary Salts |
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| These salts contain atoms of three elements only. |
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| h) Complex Salts |
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| Salts that dissociate in water to give one simple ion and one complex ion are called complex salts. |
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