JEE Advanced Model Paper 8 with solutions for online practice

A black, water insoluble powder (A) liberates yellowish green gas (B) on treatment with conc.HCl and (A) dissolves to give a clear solution. Solid (A) when heated with PbO2 and HNO3 (or) sodium bismuthate & H2SO4 gives a purple solution (C). The purple solution is due to theformation of