Aluminium oxide is amphoteric oxide because it shows the properties of both
acidic and basic oxides. It reacts with both acids and bases to form salt and
(b) Metals when react with acids, donate electrons to hydrogen ions
present in acid to form hydrogen atoms which combines further form hydrogen gas.
(c) Iron articles when come in contact with oxygen and
water, to form rust, a flaky substance on its surface and slowly loses its
strength. To avoid this it is painted frequently.
(d) Iron sheets are coated with zinc (galvanisation) so as
to prevent iron from
(e) When copper vessels are exposed to moist air, (they
form a green coating of basic copper carbonate
The sour substances such as lemon or tamarind juice
contain acids. These acids dissolve the coating of copper oxide or basic copper
carbonate present on the surface of tarnished vessels and make them shining
red-brown again. (1)
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