Answer:
See explanation
Explanation:
If the spot in TLC is below the solvent front, it will be observed that the spot, instead of being separated by the solvent as expected, will just dissolve away in the solvent and zero actual separation of the mixture is achieved.
If the solute is dissolved away instead of being separated by the solvent, then the experiment fails because no actual separation of the mixture is achieved.
Hence, in TLC, the spot must be applied above the solvent front so that the capillary movement of the solvent through the plate can lead to the eventual separation of the components of the mixture since the various components of the mixture will travel at different speeds through the plate.
Also, if the solvent is above the spot, the solvent may evaporate selectively from the points above the spot while separation is ongoing.
There are 1.2 hr would this current have to be applied to plate out 7. 20 g of iron .
Calculation ,
Given ; Current ( I ) = 5. 68 A
In 
, the valancy of Fe is +2 .
2 moles of 
are required for the decomposition of 1 mole of Fe .
7. 20 g of Fe in moles = 7. 20 g /55.845 g/mol =0.12 mole
x moles of are required for the decomposition of 0.128 mole of Fe .
moles of are required = 0.256 moles
Charge on 1 mole of = 96500 C
Charge on 0.256 mole of = 24704 C
Current ( I )= Q/t
t =Q / I = 24704 C/5. 68 A = 4349 sec = 1.2 hr
Therefore , there are 1.2 hr would this current have to be applied to plate out 7. 20 g of iron .
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