When `K_2 Cr_2 O_7` crystals are heated with conc. HCl, the gas evolved is

When potassium ferrocyanide crystals are heated with conc. sulphuric acid, the gas evolved is

When the nitrate is heated with conc. H_(2)SO_(4) , gas evolved is

Which potassium dichromate crystal are heated with conc. HCl

When a chloride salt is heated with conc. H_2SO_4 , HCl gas is evolved whereas when a bromide salt is heated with conc. H_2SO_4 , Br gas is evolved. Why?

When K_(2)Cr_(2)O_(7) is heated with conc. H_(2)SO_(4) and soluble chloride such as KCl :