The number of moles of K2Cr2O7 that will be needed to react completely with one mole of ferric sulphite in acidic medium is

Fe2SO331 mol ⇌  2Fe3+ + 3SO32-3 molFe3+ is already in oxidized state hence Cr2O72- is not required by  Fe3+3SO32- is oxidized to SO42- by Cr2O72- in acidic medium3S+4O3-2 +Cr2+6O7-2   + 8H+ →  2Cr+3+3S+6O4-2  +4H2O1 mole Fe2SO33 → 3 moles SO32-= 1 mole Cr2O72-