Explain the following
(a) Reactivity of Al decreases if it is dipped in HNO3.
Ans. Nitric acid is a strong oxidizing agent. Due to this, when aluminium is dipped in nitric acid, a layer of aluminium oxide is deposited on aluminium. As a result; reactivity of aluminium decreases when it is dipped in nitric acid.
(b) Carbon cannot reduce the oxides of Na or Mg
Ans. Sodium and magnesium are highly reactive metals. Hence, they have higher affinity to oxygen than to carbon. Due to this, carbon fails to reduce the oxides of sodium or magnesium.
(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
Ans. NaCl is an ionic compound. Ionic compounds do not conduct electricity in solid state. But ionic compounds are good conductors of electricity in molten state and in aqueous solution.
(d) Iron articles are galvanised.
Ans. Iron has a tendency to react with atmospheric moisture. This process is called rusting and leads to corrosion of iron. Iron articles are galvanized to prevent rusting of iron.
(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.
Ans. Na, K, Ca and Mg are highly reactive metals. They can easily form compound with most of the elements. Due to this, these metals are not found in their free state in nature.
