Question

How can you verify Faraday's First Law of Electrolysis experimentally?

Answer 1

Step 1: Faraday’s First Law of Electrolysis

It states, that during electrolysis, the amount of chemical reaction which occurs at any electrode under the influence of electrical energy is proportional to the quantity of electricity passed through the electrolyte.

Step 2: Construction

1. Let us assume that a rheostat, battery, ammeter, and key are connected in series to an electrolyte.
2. The mass of a cathode is measured and inserted into the cell.
3. A current $I_1$ is passed through time $t$.
4. Current is measured using the ammeter.
5. The mass of the cathode is measured again after removing it.
6. A deposit of $m_1$ mass is obtained.
7. The cathode is reinserted into the cell.
8. A current $I_2$ is passed through the same time $t$.
9. Another amount of deposit of mass $m_2$ is obtained.
10. The same procedure is repeated with more mass deposits, say $m_3$ and $m_4$.

Step 3: Derivation

It is experimentally found that,

$\frac{m_1}{m_2}=\frac{I_1}{I_2}$

$\therefore m\propto I\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \left(1\right)$

When the experiment is repeated again, we get

$\frac{m_3}{m_4}=\frac{t_1}{t_2}$

$\therefore m\propto t\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots .\left(2\right)$

From equations $\left(1\right)$ and $\left(2\right)$ we get,

$m\propto It$

We know that $It=q$

$\therefore m\propto q\dots \dots \dots \dots \dots \dots \dots ..\left(3\right)$

Hence, equation $\left(3\right)$ proves the Faraday’s – First Law of Electrolysis.