Final answer:
Copper reacts with nitric acid to form copper(II) nitrate, a water-soluble compound that turns blue in solution due to the arrangement of electrons in the copper d orbitals.
Step-by-step explanation:
Copper reacts with nitric acid to form water-soluble copper(II) nitrate. The reaction of copper wire with concentrated nitric acid produces several products; the blue color in the solution indicates the presence of water-soluble copper salts. When copper metal is reacted with nitric acid, it importantly forms copper(II) nitrate alongside other products such as nitrogen dioxide and water. The balanced chemical equation for copper oxide reacting with nitric acid is written as:
CuO(s) + 2HNO3(aq) → Cu(NO3)2(aq) + H2O(l)
This equation demonstrates the conversion of insoluble copper(II) oxide to soluble copper(II) nitrate when an aqueous solution of HNO3 is present.