(a) As HNO3 is an oxidising agent. So, when aluminium is dipped in HNO3 a layer of aluminium oxide is formed on the surface of the metal, which prevents it from further reactions with other compounds.
(b) Na, Mg metals are quite reactive and are present at the top of the reactivity series. Hence, their affinity towards oxygen is quite high and their oxides cannot be reduced by carbon.
(c) Ions of NaCl cannot move to carry/transport the charges in dry state due to electrostatic forces of attraction by neighboring atoms, But, they are free to move in molten state and in aqueous solution to carry the charge. So, NaCl conducts electricity in molten state as well as in aqueous solution but not in dry state.
(d) Galvanisation is required as it prevents iron articles from corrosion in galavanistion a thin layer of zinc is formed over the iron articles by dipping them in molten zinc, which prevents iron from corrosion.
(e) Metals like Na,K,Ca and Mg are quite reactive so, they cannot exist in free state and hence they are found in nature in form of their compounds
Example: NaCl, KCl , CaCO3 ,MgO etc.
(a) The equations involved are written as:
2Cu2S (s) + 3O2 (g)→ 2Cu2O (s) + 2SO2 (g) [Oxidation]
2Cu2O (s) +Cu2S(s) → 6Cu (s) + SO2 (g) [Reduction]
(b) The process of electrolytic refining is explained as:
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