Faraday propounded two laws about electrolysis.
1st Law
It states that the mass of an element deposited during electrolysis is directly proportional to the quantity of electric charge passed through it. M α Q. M = EQ.
Where M = mass, Q = charge, E = electrochemical equivalent.
2nd Law
It states that if the same quantity of electricity is passed through different electrolytes, that the relative number of moles of the elements discharged are inversely proportional to the charges on the ions of the elements.
N.B: One Faraday = 96500c
Also, the amount of charge to liberate an atom of element = the ionic charge value X Faraday (96500c).
Example: (1)
Calculate the mass of silver deposited when a current of 2.6A is passed through a solution of a silver salt for 70 minutes. (Ag = 108; IF = 96500c).
Solution
Ag+ + e– …………………………Ag(s)
103g IF = 108g = 96500c
Since Q = It = 2.6 x 70 x 60
Since 96500 = 108g
2.6 x 70 x 60 = x
Xg = (2.6 x 70 x 60 x 108) / 96500
:. The mass of silver deposited is 12.22g
Example: (2)
Calculate the mass of an element deposited at the electrode during electrolysis by passing of 3A for 2 minutes through the electrolyte
Solution:
M α Q
M = EQ
Q = 3 x 2 x 60 = 360
M = 2 x 360 = 720g