SPM Chemistry

Chemical Properties of Bases/Alkalis

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Chemical Properties of Bases/Alkalis

  1. Alkalis react with acids to form a salt and water — this is a neutralisation reaction:
  2. Alkalis, when warmed with ammonium salts, give off ammonia gas:

Reaction between Alkalis and Acids

Acid + Alkali → Salt + Water

Example:
Potassium hydroxide + Nitric Acid → Potassium Nitrate + Water

KOH + HNO3  → KNO3  +  H2O

Alkali heat with Ammonium Salts

Ammonium Salt + Alkali → Salt + Ammonia + Water


Example:
Ammonium Chloride + Sodium Hydroxide → Sodium chloride + Water + Ammonia

NH4Cl + NaOH → NaCl +  H2O + NH3

More examples:

2NH4Cl +    Ca(OH)2  → CaCl2 + 2H2O + 2NH3
(NH4)2SO4 + 2NaOH→ Na2SO4 + 2H2O+ 2NH3

Ammonia as an Alkali

  1. By nature, ammonia is a covalent compound.
  2. Ammonia exists as gas at room temperature.
  3. Ammonia gas is soluble in water.
  4. Physical properties of ammonia:
    1. Pungent smell
    2. Colourless
    3. Turn litmus from red to blue