Metals react with water to form their oxides or hydroxides. State the special name given to the metallic oxides which dissolve in water.
a. Formation of oxide:
When copper is heated in air, it combines with oxygen to form copper oxide, black oxide. The reaction is:
Formation of hydroxide:
Most metal oxides are insoluble in water but some of these dissolve in water to form alkalies (hydroxides). When sodium oxide dissolved in water, it produces NaOH (sodium hydroxide). The reaction is:
Na2O + H2O → 2NaOH
When metallic oxide reacts with both acids as well as bases are known as amphoteric oxides. For ex-
2Al2O3 + 6HCl → 2AlCl3 + 3H2O
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