Arrange the oxides CrO, CrO₃ and Cr₂O₃ in the decreasing order of acidic strength

CONCEPT:

Acidic Strength of Oxides

• The acidic strength of oxides generally increases with the oxidation state of the central atom.
• Oxides of metals tend to be basic, while oxides of non-metals tend to be acidic. Transition metals, like chromium, can form oxides that have varying acidic or basic properties based on their oxidation states.

EXPLANATION:

• For chromium oxides:
  • CrO (Chromium(II) oxide) has chromium in a +2 oxidation state.
  • Cr₂O₃ (Chromium(III) oxide) has chromium in a +3 oxidation state.
  • CrO₃ (Chromium(VI) oxide) has chromium in a +6 oxidation state.
• The acidic strength of these oxides increases with the oxidation state of chromium:
  • CrO is basic due to the low oxidation state of +2.
  • Cr₂O₃ is amphoteric (can act as both acid and base) due to the intermediate oxidation state of +3.
  • CrO₃ is highly acidic due to the high oxidation state of +6.
• Therefore, the decreasing order of acidic strength of these oxides is:
  • CrO₃ > Cr₂O₃ > CrO

Therefore, the correct answer is option 1: CrO₃ > Cr₂O₃ > CrO.