cadmium amalgam is prepared by electrolysis of a solution of CdCl2 using Hg cathode. how long shud current of 5 ampere be passed to prepare 12% Cd-Hg amalgam on a cathode of 2 gm Hg(Cd=112.4(molecular mass))

Dear Student,

Please find below the solution to the asked query:

Amount of Cd required by 2 g Hg to prepare 12% amalgam = 12/88 × 2 = 0.273 g
Cd2+ + 2e- →  Cd 

To deposit 1 mole or 112.4 g of Cd we require  2 moles of electrons, hence 2 × 96500 C of charge area required

Charge required to deposit 0.273 g of Cd  = (2x96500/112.40) × 0.273 = 468.76 Coulomb 

Charge = current (A) x time (s)

time = 468.76 Coulomb ‚Äč/ 5 A = 93.75 seconds

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