Explain the following (4) (a) Reactivity of Aluminium 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.
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Reason for the following:
Explanation:
- Decrease in reactivity has been observed when aluminium is dipped in nitric acid. This is because of the formation of a layer of aluminium oxide. Nitric acid is a strong oxidizing agent and the formation of aluminium oxide layer prevents further reaction of aluminum and that is why reactivity of aluminum decreases.
- Carbon does not displace the oxides of sodium or magnesium. This is because the sodium and magnesium metal is highly reactive. Carbon is less reactive metal according to reactivity series and carbon is a strong oxidizing agent. Thus, carbon cannot reduce the strong metal oxides like Na or Mg.
- In solid state, sodium chloride does not conduct electricity because sodium chloride is a ionic compound and in solid state ions are fixed in a lattice or in closed packing. It conduct electricity in molten state and in aqueous solution because in aqueous solution as well as in molten state ions are free to move.
- Rusting of iron happens when iron converts into its oxide in the presence of air, moisture and water. To prevent it from rusting galvanization is used. During galvanization, a layer of zinc is applied to the iron object which prevent it from rusting.
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