Caption:
Copper reacts with nitric acid. Copper metal (Cu) coil is placed in a test tube with concentrated (17M) nitric acid (HNO3). Copper is oxidized to form copper nitrate (Cu(NO3)2) and brown nitrogen dioxide gas (NO2) bubbles: Cu + HNO3 -> Cu(NO3)2 + NO2 + H2O. The progression of the reaction is shown in this sequence.