1. Bases are compounds which react with acid to form a salt and water as only products.
  2. Bases that soluble in water are called alkalis.
  3. In aqueous solution, alkali it produces hydroxide ions (OH). In short, alkalis are substances that form hydroxide ions (OH(aq)) in water
    Sodium hydroxide NaOH gives Na+(aq) and OH(aq) ions,

    NaOH → Na+ + OH

    calcium hydroxide Ca(OH)2 gives Ca2+(aq) and 2OH(aq)  ions.

    Ca(OH)2 → Ca2+ + 2OH

    Ammonia give NH4+ and OH

    NH3 + H2O → NH4+ + OH

    [Note: an alkali is a base soluble in water.]

  4. In alkaline solution there are more OH ions than H+ ions.