Question

Give the balanced equations for the reaction with three different amphoteric oxides with a caustic alkali. Write your observation if any.

Answer 1

1. \[\ce{\underset{White}{ZnO} + 2NaOH ->\underset{Sodium zincate(Colourless)}{Na2ZnO2 + H2O}}\]

Observation: White zinc oxide solid dissolves in the hot caustic alkali solution to form a clear, colourless solution of sodium zincate.

2. \[\ce{\underset{White}{Al2O3} + 2NaOH ->\underset{Sodium aluminate(White)}{2NaAlO2 + H2O}}\]

Observation: Insoluble white aluminium oxide powder dissolves in the caustic alkali to form a clear, colourless solution of sodium aluminate.

3. \[\ce{\underset{Yellow}{PbO} + 2NaOH ->\underset{Sodium plumbite(Colourless)}{Na2PbO2 + H2O}}\]

Observation: Yellow or red lead oxide powder reacts and dissolves in the warm caustic alkali to yield a clear, colourless solution of sodium plumbite.