Answer :
b. his method is unsound because it changes the compounds involved.
If you had Fe (II) Oxide and switched the II to III the compound of Fe (III) Oxide is entirely different. i.e. FeO is Iron II and Fe2O3 is Fe III.
If you had Fe (II) Oxide and switched the II to III the compound of Fe (III) Oxide is entirely different. i.e. FeO is Iron II and Fe2O3 is Fe III.