Assume that impure copper contains only iron, silver and a gold as impurities. After passage of `140A`, for `482.5` sec, of the mass of the anode decreased by `22.260g` and the cathode increased in mass by `22.011g`. Estimate the % iron and % copper originally present.

Options

A. `Cu =98.88%, Fe = 0.85%`
B. `Cu =0.85%, Fe = 98.88%`
C. `Cu =90%, Fe = 10%`
D. `Cu =60%, Fe = 40%`

Answer

`Cu =98.88%, Fe = 0.85%`

Explanation

At cathode only pure copper is deposited so % of
`Cu = (22.011)/(22.26) xx 100 = 98.88%`
Charge passed
`=140 xx 482.5 = 67550` colombs
`= (67550)/(96500) = 0.7` Faraday
Faraday used fot reduction of `Cu =(22.011 xx 2)/(63.5) = 0.69326`
so Farday used for iron `=0.7 - 69326 = 0.00674 F`
mass of iron
`= (0.00674 xx 56)/(2) = 0.1887 g`
`% of Fe = (0.1887)/(22.26) xx 100 = 0.847%`