Faraday’s Laws of Electrolysis
Faraday’s Laws of Electrolysis give the relationship between the
amount of material liberated at the electrode and the amount of electric energy
that is passed through the electrolyte.
First Law of Electrolysis : It states that the amount of any substance
that is liberated at an electrode during electrolysis is directly proportional
to the quantity of electricity passed through the electrolyte.
W µ Q \ Q = I
´ t
\ W µ I
´ t
Therefore, W = Z ´ I ´
t
Where W = Weight of substance deposited or liberated at the electrode
Z = is the constant (electrochemical equivalent)
I = current strength in ampere
t = time in second
Second Law of Electrolysis : It states that when the same amount of
electricity is passed through different electrolytes, the amount of different
substances deposited or liberated are directly proportional to the equivalent
weight of the substances. Consider two cells connected in a series containing
copper sulfate and silver nitrate and if the electric current passes through
both the cells then,
weight of silver deposited µ Equivalent weight of
silver
and weight of copper deposited µ Equivalent weight
of copper
\WAg EAg
WCu = ECu
The basic unit of electrical charge is called Faraday which is defined
as the charge on one mole of electrons. Electrolysis of sodium iodide solution
to find out Faraday can be given as follows :
Na (l) + e- ® Na (l) Reduction
2 I - (l) ® I2 (s) + 2e- Oxidation
Net reaction 2Na(l) + 2I-(l) ® 2Na(l)
+ I2 (s) (Redox)
The passage of 1 Faraday of charge will produce 1 mole of Sodium metal and 2
Faraday of charge will produce 1 mole of Iodine.
The passage of 2 Faraday of charge will give 2 moles of sodium metal and 1
mole of iodine.
|
