Question

What happens when concentrated nitric acid is heated and copper is added to it?

Answer 1

Hot concentrated nitric acid acts as a strong oxidizing agent. When copper is added to it, a vigorous reaction occurs, a blue-coloured solution of Copper nitrate is formed, and dense reddish-brown fumes of nitrogen dioxide (NO₂) gas are evolved.

\[\ce{Cu + 4HNO3 (conc.) ->[\Delta] Cu(NO3)2 + 2H2O + 2NO2 ^}\]