Question

Given below are two statements : 
Statement I : CrO\( _3 \) is a stronger oxidizing agent than MoO\( _3 \) 
Statement II : Cr(VI) is more stable than Mo(VI) In the light of the above statements, choose the correct answer from the options given below

• A. Statement I is false but Statement II is true
• B. Statement I is true but Statement II is false
• C. Both Statement I and Statement II are true
• D. Both Statement I and Statement II are false

Hint:

Remember the trends in oxidizing power and stability of oxidation states down a group in transition metals. For oxides in higher oxidation states, oxidizing power typically decreases down the group, while the stability of higher oxidation states often increases down the group for heavier elements.

Answer 1

The Correct Option is B

To determine the correctness of the given statements, let's analyze each one in detail:

Statement I: CrO₃ is a stronger oxidizing agent than MoO₃

This statement is true. Chromium trioxide (CrO₃) is known to be a powerful oxidizing agent. It readily accepts electrons due to its high oxidation state of +6, which makes it an effective electron acceptor and oxidizing agent. In contrast, Molybdenum trioxide (MoO₃) is a less effective oxidizing agent in comparison. The difference in oxidizing strengths can be attributed to the electronic configuration and periodic trends; Cr is generally a stronger oxidizing agent than Mo.

Statement II: Cr(VI) is more stable than Mo(VI)

This statement is false. The stability of oxidation states tends to decrease as you move down a group in the periodic table. Chromium in the +6 oxidation state (Cr(VI)) is not as stable as Molybdenum in the +6 oxidation state (Mo(VI)). Molybdenum's higher atomic number and lower position in the group make Mo(VI) more stable compared to Cr(VI), which is more prone to reduction and disproportionation.

Conclusion:

Based on the above analysis, Statement I is true but Statement II is false. Therefore, the correct answer is: Statement I is true but Statement II is false.

Answer 2

Statement I: CrO\( _3 \) is a stronger oxidizing agent than MoO\( _3 \) In the same group of transition metals, the oxidizing power of oxides in higher oxidation states generally decreases down the group. 
Chromium (Cr) and Molybdenum (Mo) belong to Group 6. CrO\( _3 \) has Cr in the +6 oxidation state (Cr(VI)), and MoO\( _3 \) has Mo in the +6 oxidation state (Mo(VI)). Due to the smaller size and higher electronegativity of Cr compared to Mo, Cr(VI) is more prone to reduction to lower oxidation states, making CrO\( _3 \) a stronger oxidizing agent than MoO\( _3 \). 
Therefore, Statement I is true. Statement II: Cr(VI) is more stable than Mo(VI) Down a group in transition metals, the stability of higher oxidation states generally decreases for the elements in the first row (like Cr) compared to the elements in the second and third rows (like Mo and W). 
This is due to the inert pair effect becoming less significant and the ability to form stable compounds in higher oxidation states increasing down the group for heavier elements. Consequently, Mo(VI) and W(VI) are generally more stable in their oxide forms (MoO\( _3 \), WO\( _3 \)) than Cr(VI) in CrO\( _3 \), which tends to be a strong oxidizing agent and readily reduced. 
Therefore, Statement II is false. In conclusion, Statement I is true, but Statement II is false. This corresponds to option (2).