Three electrolytic cells A,B,C containing solutions of ZnSO4, AgNO3 and CuSO4, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?
Given -
I = 1.5 A
W = 1.45 g of Ag
t = ?
n = 1
Equivalent weight is Ag, EAg = 
= 180
Equivalent weight is Cu, ECu = 
= 31.75
Equivalent weight is Zn, EZn= 
= 32.5
Using Faraday’s second law of electrolysis, to find the mass of Cu and Zn, we use Equation 1,
→ Equation 1
⇒ 
∴ WCu = 0.426 g
⇒ 
∴ WZn = 0.436 g
To find the time of current flow, using Faraday’s first law of electrolysis we get,
M = Z ×I ×t ⇒ Equation 2
∵ Z = 
, Equation 2 becomes,
M = 
t = 
t = 864 seconds.
The time of current flow, t = 864 seconds, the mass of Cu is 0.426 g and mass of Zn is 0.436 g