Question

Which of the following metal forms amphoteric oxide?
A.) Copper
B.) Silver
C.) Aluminium
D.) iron

Answer 1

Hint: Try to recall that amphoteric oxides are those which react with both acid and base to give salt and water. The elements forming these oxides are neither strongly electropositive or electronegative. Now by using this you can easily find the correct options from the given options.

Complete step by step solution:
It is known to you that amphoteric oxides are formed by those elements which have a tendency to gain as well as donate electrons during a chemical reaction and they react with both acid as well as base to form salt and water.
Amphoteric oxides are those metallic oxides which show acidic as well as basic nature.
It has been seen that oxides of aluminium are amphoteric in nature. This happens because in acidic conditions, protons in the solution will protonate the oxygen of aluminium oxides, forming water and aluminium’s corresponding salt whereas in basic conditions, hydroxide ions promote the formation of more hydroxide ions from aluminium oxide’s oxygen forming a hydrated aluminate complex and water.
Therefore, from the above discussion we can easily say that option C is the correct option to the given question.

Note: It should be remembered to you that electropositive elements like metals form basic oxides whereas electronegative elements like non metals form acidic oxides.
Also, you should remember that aluminium carries high positive charge in its oxides which makes it attracted to the hydroxyl group of water. So, it can react with water to release protons instead of hydroxyl groups.