(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 the 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.

Answers:

(a) Reactivity of Al decreases if it is dipped in HNO3

Reason:

Nitric acid (HNO₃) is a strong oxidizing agent and the reactivity of the aluminium when a layer of aluminium oxide gets deposited.

(b) Carbon cannot reduce the oxides of Na or Mg

Reason:

Na and Mg are highly reactive metals which has a higher affinity to oxygen than carbon.

(c) NaCl is not a conductor of electricity in the solid-state whereas it does conduct electricity in aqueous solution as well as in molten state

Reason:

NaCl can conduct electricity only in aqueous and molten state but not in solid satate.

(d) Iron articles are galvanised.

Reason:

 Iron is galvanized to avoid the rusting.

(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.

Reason:

Na, K, Ca and Mg can form compounds with all the elements and are highly reactive.