Consult the table of standard electrode potentials and suggest three substances that can oxidise ferrous ions under suitable conditions
For a substance to oxidise Fe2+to Fe3+ ion, it must have high reduction potential than Fe3+. The reduction potential of Fe3+ to Fe2+ reaction is 0.77V, the substances which have reduction potentials higher than this value will oxidise Fe2+ ions. Comparing the values, from the table:
F2,Br2,Cl2,H2O2 can oxidise ferrous ions.