Question

Explain the Faraday second law of electrolysis.

Answer 1

The mass of the chemical deposited due to electrolysis is not only proportional to the quantity of electricity that passes through the electrolyte, but it also depends upon some other factor. Every substance will have its own atomic weight. So for the same number of atoms, different substances will have different masses. Again, how many atoms deposited on the electrodes also depends upon their valency. If valency is more, then for the same amount of electricity, the number of deposited atoms will be less whereas if valency is less, then for the same quantity of electricity, more number of atoms to be deposited. So, for same quantity of electricity or charge passes through different electrolytes, the mass of deposited chemical is directly proportional to its atomic weight and inversely proportional to its valency.
Faraday's second law of electrolysis states that, when the same quantity of electricity is passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight.
Equivalent Weight:
The chemical equivalent or equivalent weight of a substance can be determined by Faraday’s laws of electrolysis and it is defined as the weight of that subtenancy which will combine with or displace the unit weight of hydrogen. The chemical equivalent of hydrogen is, thus, unity. Since valency of a substance is equal to the number of hydrogen atoms, which it can replace or with which it can combine, the chemical equivalent of a substance, therefore may be defined as the ratio of its atomic weight to its valency.
Thus chemical equivalent $=\frac{Atomicweight}{Valency}$