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p-Block elements form acidic, basic, and amphoteric oxides. Explain each property by giving two examples, and also write the reactions of these oxides with water.

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The oxides of p-block elements show acidic, basic and amphoteric properties due to the following factors:

  1. Ionisation enthalpy: Higher the ionisation enthalpy of an element, stronger the acid formed by that element. If ionisation enthalpy of an element is high, then its oxide will be acidic in nature, if it is low, then it will be basic in nature, and if it is intermediate, its oxide will be amphoteric in nature.
  2. Electronegativity: Higher the electronegativity of the element, more acidic its oxide is. For instance, N_{2}O_{3} is more acidic than B_{2}O_{3}
  3. Oxidation states: Higher the oxidation state of the elements, the stronger will be its acid. For instance, SO_{3} is a stronger acid than SO_{2}

Reaction with water

B_{2}O_{3}+3H_{2}O\rightleftharpoons 2H_{3}BO_{3}

Boron Trioxide               Orthoboric acid

B(OH)_{3}+ H-OH\rightarrow [B(OH)_{4}]^{-}+H^{+}

Al_{2}O_{3} is amphoteric in nature. It is insoluble in water but dissolves in alkalis and reacts with acids.

Al_{2}O_{3} +2NaOH\overset{\Delta }{\rightarrow}2NaAlO_{2}+H_{2}O

Aluminium trioxide                   Sodium meta-aluminate

Al_{2}O_{3} +6HCl\overset{\Delta }{\rightarrow}2AlCl_{3}+3H_{2}O

                                       Aluminium Chloride

Ti_{2}O is as basic as NaOH due to its lower oxidation state (+1).

Ti_{2}O+2HCl\rightarrow 2TiCl+H_{2}O


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