COMEDK · Chemistry · 23. d and f Block Elements

What is the spin only magnetic moment of the metal ion in \(\mathrm{P}\) and the oxidation number of Sulphur in the oxidised product \(\mathrm{Z}\) ?

A \(\mu=5.00 \mathrm{BM} \quad\) Oxidation number \(=0\)
B \(\mu=1.732 \mathrm{BM} \quad\) Oxidation number \(=+6\)
C \(\mu=0 \quad\) Oxidation number \(=+4\)
D \(\mu=5.92 \mathrm{BM} \quad\) Oxidation number \(=+2\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\mu=1.732 \mathrm{BM} \quad\) Oxidation number \(=+6\)

Step-by-step Solution

Detailed explanation

Pyrolusite is \(MnO_2\). When fused with \(KOH\) and \(KNO_3\), it forms potassium manganate (\(K_2MnO_4\)), which is compound \(P\). \(2MnO_2 + 4KOH + O_2 \rightarrow 2K_2MnO_4 + 2H_2O\). In \(K_2MnO_4\), the manganese ion is \(MnO_4^{2-}\). The oxidation state of \(Mn\) 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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