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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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Answer» Solution :In p-block, when we move from LEFT to right in a period, the acidic character of the oxides increases due to increase in electronegativity. E.g, `2^(nd)` period `:B_(2)O_(3) lt CO_(2) lt N_(2)O_(3)` acidic nature increases. `(ii) 3^(rd)` perido `Al_(2)O_(3) lt SiO_(3) lt P_(4)O_(10) lt SO_(3) lt Cl_(2) O_(7)` acidic character increases. On moving down the group, acidic character decreases and BASIC character increases. e.g., (1) Nature of oxides of 13 group elements : `underset("Weakly acidic")(B_(2)O_(3))underset("Amphoteric")ubrace(Al_(2)O_(3)GHa_(2)O_(3)) underset("Basic")(In_(2)O_(3)) underset("Strongly basic")(Tl_(2)O)` (ii) Natureof oxides of 15 group elements : `underset("Strongly acidic")(N_(2)O_(5)) underset("Moderately acidic")(P_(4)O_(10)) underset("Amphoteric")(As_(4)O_(10))underset("amphoteric")( Sb_(4)O_(10)) underset("Basic")(Bi_(2)O_(3))` Among the oxides of same element, higher the oxidation state of the element, stronger is the acid. e.g., `SO_(3)` is a stronger acid than `SO_(2)`. `B_(2)O_(3)` is weakly acidic and on dissolution in water, it forms orthoboric acid. Orthoboric acid does not act as a protonic acid (it does not ionise) but acts as a weak Lewis acid. `underset("Boron trioxide")(B_(2)O_(3))+ 3H_(2)O hArr underset("Orthoboric acid")(2H_(3)BO_(3))` `B(OH)_(3)+H-OH to [B(OH)_(4)]^(-)+H^(+)` `Al_(2)O_(3)` is amphoteric in nature. It is insoluble in water but dissolves in alkalies and reacts with acids. `underset("Aluminium trioxide")(Al_(2)O_(3))+2NAOH overset(Delta)to underset("Sodium metal aluminate")(2NaAlO_(2))+H_(2)O larr Al_(2)O_(3) +6HCI overset(Delta)to underset("Aluminum Chlorid")(2AlCl_(3))+3H_(2)O` `Tl_(2)O` is as a basic as NaOH due to its lower oxidation state (+1). `Tl_(2)O+2HCI to 2TICI+H_(2)O` `P_(4)O_(10)` on reaction with water gives orthophosphoric acid. `underset("Phosphorus pentoxide")(P_(4)O_(10)) +6H_(2)O to underset("Orthophosphoric acid")(4H_(3)PO_(4))` `Cl_(2)O_(7)` is strongly acidic in nature and on dissolution in water, it gives perchloric acid. `underset("Dichlorine heptoxide")(Cl_(2)O_(7))+H_(2) toO underset("Perchloric acid")(2HCIO_(4))` |
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