CuS is dissolved in dil. HNO3. Balanced equation with correct products is

CuS (black ppt.) on boiling with HNO3 results in the formation of colloidal S and blue colored solution of CuNO32.CuS+HNO3→Cu(NO3)2+ S +NO+H2O     Oxidation half reaction CuS+HNO3→Cu(NO3)2+S  CuS+2HNO3→Cu(NO3)2+S+2H++2e----(1)     Reduction half reaction HNO3→NO+H2O HNO3+3H++3e-→NO+2H2O ---(2) (1)×3+(2)×2⇒3CuS+8HNO3→3Cu(NO3)2+3S+2NO+4H2O