Question

State Faraday’s first law of electrolysis.

Answer 1

Hint: To answer this question we must first recall the process of electrolysis. Whenever an electrolyte like metal sulfate is diluted in water, its molecules split into positive and negative ions. The positive ions move to the negative terminal and undergo reduction whereas the negative ions move to the positive terminal and undergo oxidation.

Complete step by step answer:
Faraday’s laws of electrolysis are quantitative (mathematical) relationships that describe these two phenomena of electrolysis.
From the explanation, it is clear to us that the flow of current through the external battery circuit depends on the number of electrons getting transferred from negative electrode i.e. cathode to the cations.
Let us assume that the cations have a valency of two like $C{u^{ + + }}$ then for every cation, there would be two electrons transferred from cathode to cation. We know that every electron has negative electrical charge $- 1.602 \times {10^{ - 19}}$ Coulombs and is denoted by $^{\, - }e$. So for disposition of every Cu atom on the cathode, there would be $^{\, - }2e$ charge transfers from cathode to cation.
Now say for t time there would be a total “n” number of copper atoms deposited on the cathode, so total charge transferred would be $^{\, - }2ne$ Coulombs. Mass m of the deposited copper is obviously a function of the number of atoms deposited. So, it can be concluded that the mass of the deposited copper is directly proportional to the quantity of electrical charge that passes through the electrolyte.
Thus, Faraday’s First Law of electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.
i.e. mass of chemical deposition:
$m\, \propto \,Quantity\,of\,electricity,Q \to m = Z \times Q$

Note: Michael Faraday had also established another law of electrolysis which is an extension of the law we learned above. It states that for the 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.