Question

which of the following statements are incorrect? 
A. All the transition metals except scandium form MO oxides which are iconic 
B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc₂O₃ to Mn₂O₇ 
C. Basic character increases from V₂O₃ to V₂O₄ to V₂O₅ 
D. V₂O₄ dissolves in acids to give VO salts 
E. CrO is basic but Cr₂O₃ 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

Answer 1

The Correct Option is B

To determine the incorrect statements, let's analyze each option.

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

Transition metals generally form oxides in which oxygen is in the -2 state. Most transition metal oxides are ionic, except for some cases like Sc₂O₃, which is more covalent. Thus, this statement is incorrect. However, since we need two incorrect statements, we will keep analyzing.

B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc₂O₃ to Mn₂O₇.

For transition metals, the maximum oxidation state is related to their group number: Sc (III), Ti (IV), V (V), Cr (VI), and up to Mn (VII). This statement is correct.

C. Basic character increases from V₂O₃ to V₂O₄ to V₂O₅.

The basic character of oxides generally decreases with an increase in oxidation state. Thus, V₂O₅ is more acidic compared to V₂O₃. Therefore, this statement is incorrect.

D. V₂O₄ dissolves in acids to give VO salts.

VO salts imply V in the +2 oxidation state as VO²⁺. However, V₂O₄ generally forms VO₂+ when dissolved in acid, indicating V in the +4 state. This statement is incorrect.

E. CrO is basic but Cr₂O₃ is amphoteric.

CrO (chromium(II) oxide) is indeed basic, while Cr₂O₃ is known to be amphoteric, reacting with both acids and bases. Therefore, this statement is correct.

Upon analyzing the statements, C and D are incorrect. Hence, the correct answer is: C and D only.