NEET 2023 — Chemistry solution

NEET2023Chemistry

Which of the following statements are INCORRECT?

A. All the transition metals except scandium form MO oxides which are ionic.

B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc $_{2}$ O $_{3}$ to Mn $_{2}$ O $_{7}$ .

C. Basic character increases from V $_{2}$ O $_{3}$ to V $_{2}$ O $_{4}$ to V $_{2}$ O $_{5}$ .

D. V $_{2}$ O $_{4}$ dissolves in acids to give $VO_{4}^{3 -}$ salts.

E. CrO is basic but Cr $_{2}$ O $_{3}$ is amphoteric.

Choose the correct answer from the options given below:

A
B and D only
B
C and D only
C
B and C only
D
A and E only

Solution

Statement C is wrong: as the oxidation state of V rises ( $+ 3 \to + 4 \to + 5$ ), the oxide becomes more acidic, not more basic. So V $_{2}$ O $_{3}$ is basic, V $_{2}$ O $_{4}$ is amphoteric, V $_{2}$ O $_{5}$ is acidic.

Statement D is wrong: $VO_{4}^{3 -}$ is the salt of V $^{+ 5}$ , formed from V $_{2}$ O $_{5}$ , not V $_{2}$ O $_{4}$ . V $_{2}$ O $_{4}$ dissolves in acids to give V $^{4 +}$ (specifically $VO^{2 +}$ ) salts.

A, B, E are correct.

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