Choose the correct statements from the following
A. Mn₂ O₇ is an oil at room temperature
B. V₂ O₄ reacts with acid to give VO₂ ²⁺
C. CrO is a basic oxide
D. V₂ O₅ does not react with acid
Choose the correct answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Check each vanadium ion against the +4 state of V₂O₄, and recall that V₂O₅ is amphoteric.

1. Oxide character trend. For a transition metal, the oxide in the lowest oxidation state is basic and the one in the highest is acidic. Oxides in between are amphoteric. Higher-state oxides are also more covalent, so some are liquids.

   Statement	Oxidation state	What really happens	Verdict
   A: Mn₂O₇	Mn is +7	Covalent molecular oxide, a green oil at room temperature	Correct
   B: V₂O₄	V is +4	Dissolves in acid to give VO²⁺ (V is +4), not VO₂²⁺	Wrong
   C: CrO	Cr is +2	Lowest oxidation state of Cr, so the oxide is basic	Correct
   D: V₂O₅	V is +5	Amphoteric: reacts with acid to give VO₂⁺ and with alkali to give vanadate	Wrong

2. Why B fails. In VO₂²⁺, vanadium would be +6, since x - 4 = +2. Vanadium has only 5 valence electrons and cannot go above +5. Dissolving the oxide in acid also keeps the oxidation state at +4, so the ion formed is VO²⁺.
3. So. Only A and C are correct, which is option (c).

The idea to keep. Low oxidation state oxides are basic and high ones are acidic, with amphoteric oxides in between. To check an ion formula, work out the metal's oxidation state and make sure it matches the oxide it came from.

Answer from the NTA final answer key. Solution by PrepWiser.