Action of potassium dichromate (VI) on iron (II) ions (Fe2+):
Answer Text: Action of potassium dichromate (VI) on iron (II) ions (Fe2+):(i). Procedure:- A solution containing iron (II) ions is added into a solution of oxidized potassium dichromate (VI).(ii). Observations:- The orange solution of potassium dichromate turns green.(iii). Explanations:- The iron (II) ions are oxidized to iron (III) ions- The chromium (VI) ions (orange) are reduced to chromium (III) ions- This is thus a REDOX reaction.Note:-The oxidation number of dichromate ions in K2Cr2O7 decreases from 6 to 3 (in Cr3+) hence reduction; while oxidation number of iron increasesfrom 2 (in Fe2+) to 3 (in Fe3+); hence oxidation;-The presence of Fe3+ at the end of the reaction can be detected by adding sodium hydroxide solution to form a red brown precipitate of Fe(OH)3;