LOKESH DAS

i. Action with moist air:  After long exposure to moist air, a green layer of its basic carbonate is formed over it.

2Cu + H₂O + CO₂ + O₂ ---------------> CuCO₃.Cu(OH)₂   

ii. Action of Conc. H₂SO₄ : When heated with conc. H₂SO₄Sulphur dioxide gas is formed.

Cu +  2H₂SO₄ -------------------> Cu(NO₃)₂ + 2NO₂ + 2H₂O

Copper sulphide contains some amount of iron sulphide as impurities which is called copper matte.
Copper matte mainly consists of cuprous sulphide and little ferrous sulphide.