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The d-And-f-Block Elements
Question
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Indicate the steps in the preparation of KMnO4 from pyrolusite ore.

Answer

Pottassium Permanganate (KMnO4) is prepared from Pyrolusite ore (MnO2). The finely powdered Pyrolusite ore (MnO2) is fused with an alkali metal hydroxide like KOH in the presence of air or an oxidizing agent like KNO3 to give the dark green potassium Manganate (K2MnO4). Potassium manganate disproportionate in a neutral or acidic solution to give potassium permanganate.

2 MnO2 + 4 KOH + O2 ----------> 2K2MnO4 + 2H2O

3 MnO42- + 4H+ ------------> 2MnO4- + MnO2 + 2H2O
Commercially potassium permanganate is prepared by the alkaline oxidative fusion ofPyrolusite ore (MnO2) followed by the electrolytic oxidation of manganate (4) ion.

2 MnO2 + 4KOH + O2 -----------> 2K2MnO4 + 2H2O

MnO42- ------(electrolytic oxidation)----> MnO4- + e-

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Some More Questions From The d-And-f-Block Elements Chapter

Silver atom has a completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?

In the series Sc (Z = 21) to Zn(Z = 30), the enthalpy of atomisation of zinc is the lowest i.e., 26, kJ mol. Why?

The E° (M2+/M) value for copper is positive (+ 0.34 V). What is possibility the reason for this? 

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

Explain why Cu+ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?