4 mole of a mixture of Mohr's salt and Fer(SO4)3 requires 500 ml of 1M K2Cr2O2 for complete oxidation in acidic medium. The mole % of the Mohr's salt in the mixture is:

Cr2O72−+6Fe2+(n=1) (Mohr's salt)+14H+⟶2Cr3++6Fe3++7H2OEquivalent of Fe2+ = moles of Mohrs salt= equivalent of K2Cr2O7=500 x 10-3 x 6 x 1 = 3.0Hence, mole per cent of Mohr's salt=34×100=75