Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

Action of potassium dichromate (VI) on iron (II) ions (#Fe^(2+)#):

Answer Text:
Action of potassium dichromate (VI) on iron (II) ions (#Fe^(2+)#):
(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 #K_2Cr_2O_7# decreases from 6 to 3 (in #Cr^(3+)#) hence reduction; while oxidation number of iron increases
from 2 (in #Fe^(2+)#) to 3 (in #Fe^(3+)#); hence oxidation;
-The presence of #Fe^(3+)# at the end of the reaction can be detected by adding sodium hydroxide solution to form a red brown precipitate of #Fe(OH)_3#;