JEE Main 2021 · 27 August · morning · Single correct · +4 / −1
The nature of oxides V₂O₃ and CrO is indexed as 'X' and 'Y' type respectively. The correct set of X and Y is :
- (a) X = basic | Y = amphoteric
X = basic Y = amphoteric - (b) X = amphoteric | Y = basic
X = amphoteric Y = basic - (c) X = acidic | Y = acidic
X = acidic Y = acidic - (d) X = basic | Y = basic
X = basic Y = basic
Answer and solution
Answer (d) X = basic | Y = basic
Solution
Chemistry ma’am · 3 steps
Find the metal's oxidation state first: a low oxidation state means a basic oxide.
- The rule. For one transition metal, the oxides become more acidic as the oxidation state rises. The lowest oxidation states give basic oxides, middle ones give amphoteric oxides, and the highest give acidic oxides.
- Oxidation states. In V₂O₃, 2x = 6, so V is +3. In CrO, Cr is +2. Both are low oxidation states for their metals.
Oxide Oxidation state of metal Nature VO +2 basic V₂O₃ +3 basic VO₂ +4 amphoteric V₂O₅ +5 amphoteric, mainly acidic CrO +2 basic Cr₂O₃ +3 amphoteric CrO₃ +6 acidic - So. V₂O₃ is basic and CrO is basic, so X = basic and Y = basic. That is option (d).
The idea to keep. Same metal, higher oxidation state, more acidic oxide. Low states give basic oxides, middle states give amphoteric oxides, and the highest state gives an acidic oxide, as with CrO, Cr₂O₃ and CrO₃.
Answer from the NTA final answer key. Solution by PrepWiser.