Question

Nitrogen cannot extend its covalency beyond four but it forms wide variety of oxides and also forms oxoacids.

1. Name the two oxoacids of nitrogen. 

2. Action of nitric acid with metals depends on many factors. Justify.

Answer 1

1. HNO_2, HNO₃

2. The product of oxidation depends upon the concentration of the acid, temperature and the nature of the material undergoing oxidation, e.g.

(a). 3Cu + 8HNO₃ (dilute) → 3Cu(NO₃)₂ + 2NO + 4H₂O

Cu + 4HNO₃(conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O

(b). Zinc reacts with dilute nitric acid to give N₂O and with concentrated acid to give NO₂. 

4Zn + 4HNO₃(dilute) → 4Zn(NO₃)₂ + 5H₂O + N₂O

Zn + 10HNO₃(conc.) → Zn(NO₃)₂ + 2H₂O + 2NO₂

Some metals (e.g., Cr, Al) do not dissolve in concentrated nitric acid due to the formation of a passive film of oxide on the surface.