Concentrated nitric acid is a colorless volatile liquid which fumes strongly in air has pungent smell. Its specific gravity at 15 degree centigrade is 1.53.
Definition and Explanation:
When one volume of concentrated HNO3 is mixed with 3 volumes of concentrated HCl, aqua regia is formed. It is employed to dissolve gold and platinum.
HNO3 (Conc.) + 3HCl (Conc.) ———————> NOCl (aq) + Cl2 (g) + 2H2O (l)
NOCl formed is decomposed giving NO and Cl2.
NOCl ——————> NO (g) + [Cl] (g)
This liberated chlorine gas converts noble metals such as gold and platinum into their water soluble chlorides.
Au (s) + 3[Cl] (aq) ——————-> 2AuCl3 (g)