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Thursday, April 14, 2022

Hall Heroult process : Electrolytic refining of Alumina ore of Aluminium:

Electrolysis of fused Alumina.
Cathode : Iron-tank lined with carbon bricks
Anode : carbon
Electrolyte : Molten [Al2O3
(5%) Na3AlF6 (85%) + CaF2 (5%) + AlF3 (5%) ]
O2 is liberated at anode and Al collects at the bottom.


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Hoope’s refining process used for electrolytic refining of Aluminium:

Cathode : carbon electrodes
Anode : Fe tank lined with carbon bricks
Electrolyte : Na3AlF6 + BaF2
Bottom layer : Impure aluminium consists of Cu, Si etc in molten state.
Middle layer : molten mixtureof Fluorides of Na, Ba,Al andAl2O3
Top layer : pure molten aluminium.
On passing the current, Al is deposited at cathode from the middle layer and an equivalent amount of Al from the bottom layer moves into the middle layer leaving behind the impurities.

Chemical refining methods:
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Wednesday, April 13, 2022

Is oxalate (C2O4)2- Weak field ligand or strong field ?


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Although [Fe(CN)6]4- is more stable (EAN-36) than [Fe(CN)6]3-(EAN-35) as par EAN rule but actually [Fe(CN)6]3 is more stable than [Fe(CN)6]4- ?

Although [Fe(CN)6]4- is more stable (EAN-36) than [Fe(CN)6]3-(EAN-35) as par EAN rule but actually  [Fe(CN)6]3 is more stable than  [Fe(CN)6]4- because in  Fe+3  Zeff will be more hence bonding between Fe+3 and -CN is more effective.

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Which complex is more stable [Ni(CN)4]4- or [Ni(CN)4]2- and why?

In general stability of Complexes is directly proportional to the magnitude of charge on central metal atom. Thus Complexes of Ni +2 are more stable than Ni0

[Ni(CN)4]4- < [Ni(CN)4]2- 

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