Question

-A lanthanoid metal oxide, LazO3 is reduced to metal by passing 8 amperes of current for 16 h. Mass of lanthanum produced is (At wt. of La = 139)2.0 kg20.25 g451.2 g221.28​

Answer 1

Explanation:

The electrode reaction are:

1 mole

Cu

2+

+

2×96500 C

2e

−

→Cu(Cathode)

Cu×Cu

2+

+2e

−

(Anode)

Thus, cathode increases in mass as copper is deposited on it and the anode decreases in mass as copper from it dissolves.

Charge passed through cell =2.68×60×60 coulomb

Copper deposited or dissolved =

2×96500

63.5

×2.68×60×60=3.174 g

Increase in mass of cathode = Decrease in mass of anode =3.174 g.