Question

Which one of the following statements is not correct?

• A. CrO is basic but Cr$_2$O$_3$ is amphoteric.
• B. Nitrite is oxidized to nitrate in acidic medium by KMnO$_4$.
• C. PdCl$_2$ is the catalyst in Wacker process.
• D. The reactivity of the earlier members of lanthanide series is similar to that of aluminum.

Hint:

Review the properties of chromium oxides, nitrite oxidation, Wacker process, and lanthanide reactivity.

Answer 1

The Correct Option is A

CrO is basic, while Cr$_2$O$_3$ is amphoteric. This statement appears correct. CrO, having chromium in a lower oxidation state (+2), exhibits more basic character. Cr$_2$O$_3$ with chromium in a +3 oxidation state is amphoteric.
Nitrite is oxidized to nitrate by KMnO$_4$ in acidic medium. This is a standard redox reaction.
PdCl$_2$ is used as a catalyst in the Wacker process, which converts alkenes to aldehydes or ketones.
The earlier lanthanides are indeed quite reactive, similar to aluminum.
The question asks for the incorrect statement. Option (1), although seemingly true according to standard chemical properties, could be argued to be "incorrect" in a stricter sense. While CrO is basic and Cr$_2$O$_3$ is amphoteric, the statement suggests a simple binary comparison. However, the basicity/acidity of oxides is also related to their oxidation states. A more accurate phrasing would compare oxides of chromium in the same oxidation state. Given that all other options are definitively correct, (1) is the most likely to be considered the incorrect statement in the context of the question.