(i)what happens to the blood red colour when oxalic acid is added to the equilibrium reaction Fe+3 + SCN- -----> [Fe(SCN)]+2 ?
(ii) what happens to the intensity of blood red colour if Hg is added to the above reaction ?
1) When the oxalic acid (H2C2O4) is added to the equilibrium reaction Fe3+ + SCN- [Fe(SCN)2+] , then oxalic acid will react with Fe3+ ions and will result in the formation of a complex compound [Fe(C2O4)]3- and thus the concentration of Fe3+ get decreased . According to Le Chatelier principle , the concentration of Fe3+ get decreased and hence formation of [Fe(SCN)2+] also get decreased and leads to decrease in the intensity of the red colour. The colour of the solution becomes light.
2) When HgCl2 solution is added to the above reaction , then Hg2+ will get react with SCN and result in the formation of the complex ion [Hg(SCN)4]2- . Hence , colour of the solution will become lighter because of the decrease in the concentration of [Fe(SCN)]2+ ion.
2) When HgCl2 solution is added to the above reaction , then Hg2+ will get react with SCN and result in the formation of the complex ion [Hg(SCN)4]2- . Hence , colour of the solution will become lighter because of the decrease in the concentration of [Fe(SCN)]2+ ion.