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

Assume that impure copper contains only iron, silver, and gold as impu

1.	Assume that impure copper contains only iron, silver, and gold as impurities. After passage of 140 A, for 482.5 s, the mass of the anode decreased by 22.260 g and the cathode increased in mass by 22.011 g. Estimate the % iron and % copper originally present.
Answer» Solution :The increase in mass of the cathode is solely due to copper. Hence, there is 22.011 g of copper (equivalance to 0.3464 mol) and therefore a total of 0.249 g of iron, gold and silver. Only the iron and copper are OXIDIZED. The gold silver fall to the bottom in the anode mud. SINCE each of the active metals REQUIRES 2 mol electrons pre mol metal, there MUST be (482.5s) `(140 C)/s(1"mol E")/(96500 C)(1 mol M^(2+))/(2 mol) = 0.3500` moles of `M^(2+)` The no. of moles of iron is therefore 0.0036, and the mass of iron is 0.20 g. The metal ios 98.88% copper and 0.90% iron.