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Assertion : Cr(VI) in the form of dichro...

Assertion : Cr(VI) in the form of dichromate in acidic medium is a strong oxidising agent where `MoO_3 and WO_3` are not.
Reason: In d-block elements higher oxidation states are favoured by heavier members.

A

If both assertion and reason are true and reason is the correct explanation of assertion.

B

If both assertion and reason are true and reason not is the correct explanation of assertion.

C

If assertion is trun but reason is false.

D

If both assertion and reason are false.

Text Solution

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The correct Answer is:
To analyze the given assertion and reason, we will break down the concepts involved step by step. ### Step 1: Understanding the Assertion The assertion states that Cr(VI) in the form of dichromate (Cr₂O₇²⁻) in acidic medium is a strong oxidizing agent, while MoO₃ and WO₃ are not. - **Dichromate as an Oxidizing Agent**: Chromium in the +6 oxidation state (Cr(VI)) is known for its strong oxidizing properties, especially in acidic conditions. This is because it can readily accept electrons and be reduced to a lower oxidation state (like Cr(III)). - **Molybdenum and Tungsten Oxides**: Molybdenum (Mo) and tungsten (W) in their +6 oxidation states (as in MoO₃ and WO₃) are generally more stable and do not exhibit the same oxidizing behavior as Cr(VI). ### Step 2: Understanding the Reason The reason provided states that in d-block elements, higher oxidation states are favored by heavier members. - **Higher Oxidation States**: As we move down the group in the periodic table, the heavier elements (like Mo and W) tend to stabilize higher oxidation states due to their larger atomic size and the involvement of d-orbitals in bonding. - **Stability of Higher Oxidation States**: This stability means that these heavier elements (Mo and W) in their +6 oxidation state are less likely to act as oxidizing agents because they are already in a stable form and do not readily accept electrons. ### Step 3: Conclusion Now, we need to evaluate the truthfulness of both the assertion and the reason: - **Assertion**: True. Cr(VI) in the form of dichromate is indeed a strong oxidizing agent in acidic medium, while MoO₃ and WO₃ are not. - **Reason**: True. It is correct that higher oxidation states are favored by heavier d-block elements. ### Final Evaluation Since both the assertion and the reason are true, and the reason correctly explains the assertion, the correct answer is: **Option A**: Both assertion and reason are true, and the reason is the correct explanation of the assertion. ---
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