Find out total number of coloured/black water insoluble compound(s) from following substances : Ag2O, HgI2, FeS, Ag3PO4, Ba(MnO4)2, Na2CrO4, PbI2, AgNO2, Ag2C2O | Redox Reactions and Volumetric Analysis β€” Chem-Mantra | Chem-Mantra