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Question
What do you understand by amphoteric oxide? Give the balanced equations for the reaction with three different amphoteric oxides with a caustic alkali. Write your observation if any.
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Solution
Amphoteric oxides : Amphoteric oxides are those compounds, which react with both acids and alkalis to form salt and water.
For example: Oxides of Aluminium, zinc and lead are amphoteric in nature.
Balanced equations for the reaction of different amphoteric oxides with a caustic alkali :
Amphoteric oxide + Alkali → Salt + Water
(a) \[\ce{\underset{\text{White}}{ZnO} + 2NaOH ->\underset{\text{Sodium zincate(Colourless)}}{Na2ZnO2 + H2O}}\]
(b) \[\ce{\underset{\text{White}}{Al2O3} + 2NaOH ->\underset{\text{Sodium aluminate(White)}}{NaAlO2 + 2H2O}}\]
(c) \[\ce{\underset{\text{Yellow}}{PbO} + 2NaOH ->\underset{\text{Sodium plumbite(Colourless)}}{Na2PbO2 + H2O}}\]
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