Chemistry question on qualitative ysis?

CuCO3 -------> CuO (black) + CO2 , Ca(OH)2 + CO2 ------>CaCO3 (s) white + H2O CuCO3 +2HCl -----> CuCl2 (green in con solution) + H2O + CO2 . CuCl2 + 2 NH3 + 2H2O ----> Cu(OH)2 .CiCl2 (basic copper chloride ,a blue precipitate.) Hence , P is CuCO3 , Q is CuO, R is CO2 ,S is CaCO3, T is CuCl2 , U is Cu(OH)2. CuCl2. The addition of HNO3 is to maintain required PH and and to avoid interference of other anions.