question_answer

  Give reasons: (i) Reactivity of Al decreases if it is dipped in HNO3                                        [NCERT Exemplar] (ii)Carbon cannot reduce the oxides of Na or Mg. (iii) Nad is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state. (iv) Metals like Na, K, Ca and Mg are never found in their free state in nature.

Answer:

                  (i) Due to the formation of a layer of oxide, i.e., Al2O3. (ii) Na or Mg are more reactive metals as compared to carbon. (iii) (in) In solid NaCI, the movement of ions is not possible due to its rigid structure but in aqueous solution or molten state, the ions can move freely. (iv) They are highly reactive.