K2Cr2O7 act as power oxidising agent in acidic medium. In the presence of H+ ions, the oxidation state of Cr froms Cr6+ is changed to Cr3+
Cr2O2-7 + 14H+ + 6- → 2Cr3+ + 6Fe3+ + 7H2O
Example: Acidified K Cr O oxidises Ferrous salts to Ferric salts.
Cr2O2-7 + 6Fe2+ +14H+ → 2Cr3+ + 6Fe3+ + 7H2O