A spoon is to be plated by silver during the electrolysis of Ag(CN)2 using spoon as cathode. Surface area of the spoon is 140cm2 and thickness is 0.01cm; calculate the time required for electroplating using current of 0.012 amp . given that the density of silver is 10.5g/ml.

Volume of spoon = Surface area × Thickness = 140×0.01 = 1.4cm3
Mass of spoon = Volume × Density = 1.4cm3× 10.5 g/cm3 = 14.7g

Reaction at cathode:
Ag+ + e-  Ag

1 mol of electrons that is 96500 C produces 108g of Ag

Now, 14.7g of Ag will be produced by = 96500108×14.7 = 13134.7 C

To find time,
Q = I ×

t = 13134.70.012 = 1094558.33s or 304.04 hours

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use density and volume to find mass of the silver to be plated on the spoon

then using this mass find the no. of moles of silver to be plated

use equation

Ag2+ -- Ag +2e-

we can see that one molecule requires 2 e-

hence one mole requires 2F charge

(F is faraday constant i.e the charge carried by 1 mole of electrons)

hence 1 mole requires 2F electrons so n moles will require 2nF electrons

charge = current x time

2nF = 0.012t

t = 0.012/2n s

= 0.06/n seconds

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