Iron exhibits +2 and +3 oxidation states. Which of the following statements about iron is incorrect?
(A) Ferrous oxide is more basic in nature than the ferric oxide.
(B) Ferrous compounds are relatively more ionic than the corresponding ferric compounds.
(C) Ferrous compounds are less volatile than the corresponding ferric compounds.
(D) Ferrous compounds are more easily hydrolyzed than the corresponding ferric compounds.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D) Only
\( \ce{Fe^{3+}} \) is smaller and more highly charged than \( \ce{Fe^{2+}} \), so it has a much higher polarising power. As the oxidation number of a metal increases, its compounds become less ionic and more covalent, and its oxides become more acidic.
(A) Ferrous oxide is more basic in nature than the ferric oxide. — A correct statement. The oxide of the lower oxidation state is more ionic and more basic; FeO is basic, while Fe2O3 is less basic (amphoteric).
(B) Ferrous compounds are relatively more ionic than the corresponding ferric compounds. — A correct statement. Fe3+ distorts the electron cloud of the anion more, so ferric compounds have more covalent character.
(C) Ferrous compounds are less volatile than the corresponding ferric compounds. — A correct statement. The more covalent ferric compounds are the more volatile ones; anhydrous FeCl3, for example, sublimes on heating, while FeCl2 is a high-melting ionic solid.
(D) Ferrous compounds are more easily hydrolyzed than the corresponding ferric compounds. — An incorrect statement. The highly polarising Fe3+ ion pulls electron density from the water molecules bound to it, so ferric salts are hydrolysed more easily and their solutions are acidic:
\( \ce{[Fe(H2O)6]^{3+} <=> [Fe(H2O)5(OH)]^{2+} + H^+} \)
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – …
