Faraday Constant:
"Faraday constant is the charge in coulombs on one mole of electrons." That is, 1 Faraday is equal to elementary charge times number of electrons in one mole of electrons. This leads us to the relationship given below:
F=Le
where, F= Faraday,
L= Avogadro constant and
e= elementary charge i.e magnitude of charge on an electron.
The unit used for Faraday Constant is C/mol or some books put it as just C.
This expression gives us the value of 96320 C for Faraday constant.
Faraday constant can also be derived by dividing the Avogadro constant by the number of electrons in one coulomb i.e precisely equal to 6.25x10^18. This leads us to a value of 96320 C.
Determination of Avogadro Constant by Electrical Method:
The rheostat is used to maintain a constant low current for a particular time. Initial mass of the cathode is noted. After the electrolysis, the change in mass of the cathode is noted. The charge passed into the cell is found by the product of current and time in seconds according to the equation:
Q=IxT
where, Q=charge passed,
I= current passed, and
T= time in seconds.
Values:
Change in mass of the cathode=M
Current in the circuit=I
Time for which the current is passed=T
Calculations:
Charge passed=IT
Charge required to deposit 1 mole of Copper=(ITx63.5)/M
Since,
Cu(aq) + 2e- = Cu(s)
2 Faraday are required to deposit 1 mole of copper. So, two Farday = (ITx63.5)/M.
Dividing (ITx63.5)/M by two will also give you the value of Faraday constant.
Now, since F=Le
L=F/e
Insert the value of F found and the value of e which is 1.6x10^-19.
This will give you the value of L which is 6.02x10^23
-Psycho Killer
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