Faraday's put forward his two laws of electrolysis in 1833.
The mass of an elements which is deposited on an electrode during electrolysis is directly proportional to the quantity of electricity which passes through the electrolyte.
If W is the amount of substance which liberates or deposited at the electrode on passing the electricity through the electrolyte and the quantity of electricity is Q, then
or W = ZQ
Z is the electrochemical constant for a given substance.
We can write the statement of the first law of electrolysis mathematically as under:
or W= Zat
If 1 ampere electric current passes through the electrolyte for 1 second then W=Z It means that on passing the current of 1 ampere for 1 second the weight of the substance deposited is equal to the electrochemical constant. For doing the calculations of electrochemical problems, we must know the units too.
unit of charge (Q) = Coulomb (C)
unit of mass (m) = Kilogram (kg)
unit of current (A) = ampere (A)
unit of electrochemical equivalent (Z) = kg/C
Faraday's first law of electrolysis is written as:
W = ZAt
W= is actually mass and not weight, as mas is commonly called weight.