d-Block Elements
The metals of the first series with the exception of copper are relatively more reactive and are oxidised by 1M H+, though the actual rate at which these metals react with oxidising agents like hydrogen ion (H+) is sometimes slow. For example, titanium and vanadium, in practice, are passive to dilute non oxidising acids at room temperature. The E° values for M2+/M indicate a decreasing tendency to form divalent cations across the series. It is interesting to note that the E° values for Mn, Ni and Zn are more negative than expected from the general trend. Whereas the stabilities of half-filled d subshell (d5) in Mn2+ and completely filled d subshell (d10) in zinc are related to their E° values; for nickel, E° value is related to the highest negative enthalpy of hydration.
V2O5 is _______ in nature which reacts with alkalies as well as acids to give ______ and _______ respectively.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Amphoteric, VO43− and VO4+ ions.
The nature of a transition metal oxide depends on the oxidation state of the metal:
Low oxidation states give basic oxides (e.g. MnO).
High oxidation states give acidic oxides (e.g. \( \ce{Mn2O7} \), \( \ce{CrO3} \)).
Intermediate cases can be amphoteric, reacting with both acids and alkalis.
In \( \ce{V2O5} \), the charge balance gives 2x + 5(−2) = 0, so V is +5. \( \ce{V2O5} \) is amphoteric, though mainly acidic:
With alkalis it gives the vanadate ion, VO43−:
\( \displaystyle \ce{V2O5 + 6NaOH -> 2Na3VO4 + 3H2O} \)
With acids it gives the dioxovanadium(V) ion, VO2+:
\( \displaystyle \ce{V2O5 + 2H^+ -> 2VO2^+ + H2O} \)
Why the other options are incorrect
Option (1) Acidic, VO43− and VO4+ ions — Incorrect. A purely acidic oxide would not dissolve in acids; \( \ce{V2O5} \) does.
Option (2) Basic, VO43− and VO4+ ions — Incorrect. A basic oxide would not react with alkalis; \( \ce{V2O5} \) does, and V in the +5 state is not basic.
Option (4) Neutral VO43− and VO2+ ions — Incorrect. A neutral oxide reacts with neither acids nor alkalis, and \( \ce{VO^{2+}} \) (the vanadyl ion) contains V in the +4 state, not +5.
Note: Options (1), (2) and (3) write the ion formed with acids as VO4+, as the NCERT textbook does in this sentence (extract below). Earlier in the same paragraph, the book names these as VO2+ salts (the dioxovanadium(V) ion), the ion shown in the equation above.
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – …
