AP EAMCET · Chemistry · Electrochemistry

Which of the following statement is not correct?

A ${Fe}^{3 +} / {Fe}^{2 +}$ redox couple has less positive electron potential than ${Mn}^{3 +} / {Mn}^{2 +}$ couple
B ${MnO}_{4}^{2 -}$ is a strong oxidizing agent but ${CrO}_{4}^{2 -}$ is not
C The second and third series of transition elements have almost similar atomic radii
D The $E^{0}$ value for ${Mn}^{3 +} / {Mn}^{2 +}$ couple is much more positive than for ${Cr}^{3 +} / {Cr}^{2 +}$ couple

Verified Solution

Answer & Solution

Correct Answer

(B) ${MnO}_{4}^{2 -}$ is a strong oxidizing agent but ${CrO}_{4}^{2 -}$ is not

Step-by-step Solution

Detailed explanation

We know that they are oxyanions of chromium in the 6+ oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible. whereas MnO42- is not strong oxidising agent because it's highest oxidation state is…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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