Explain the following:
(a) Reactivity of Al decreases if it is dipped in HNO3.
(b) Carbon cannot reduce the oxides of Na or Mg.
(c) NaCl is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state.
(d) Iron articles are galvanised.
(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.
(a) It is due to the formation of oxide layer on its surface.
(b) It is because Na or Mg are strong reducing agents, therefore, carbon cannot reduce their oxides.
(c) NaCl does not conduct electricity in solid state as it does not have free ions to move in solid state but in aqueous solution and in molten states ions are free to move.
(d) Iron articles are galvanised to protect them from rusting.
(e) It is because these metals are highly reactive and occur in the form of their compounds.