Electrolysis (continued)

It is an electrolysis where there is the dissociation of an ionic compound in aqueous solution. The electrode must be inert.

It is necessary to consider the water selfionization reaction, where H + ion and OH- ion are produced. The ionic compound is dissolved in water, forming free ions, which will produce the electric current. The four reactions must be assembled to obtain the overall reaction of this electrolysis.

In this electrolyte tank, there must be water and ionic compound dissolved. From water selfionization, H + ions and OH- ions will be formed.

If the compound is a salt, NaCl, in contact with water, will form Na + ion and Cl- ion. Positive ions will be attracted by the negative electrode and negative ions will be attracted by the positive electrode. Each pair of ions (positive and negative) will compete with each other to see which will form around their respective electrode.

There is an electrical discharge facility table between cations and anions:


Earth Alkaline
Al3+ <H + <other cations

Increasing order of cation discharge facility


Oxygenated Anions <OH- <nonoxygenated anions <halogens

Increasing order of anion discharge facility

Looking at the table, one should then compare the following ions:
- Cl- and OH-
- H + and Na +

According to the table, the Cl- (halogen) ion is easier than the OH- ion.
According to the table, H + ion is easier than Na + ion.

Then, at the electrodes, hydrogen gas (H2) and chlorine gas (Cl2).

At the pole (-) = H +
At the pole (+) = Cl-



Note that the H is formed2 and Cl2.

It also forms 2Na + and 2OH-. Together these two ions form 2NaOH.

Battery and Electrolysis Summary

Daniell Stack

Polo +

Polo -





Increase blade

Corrode the blade

Thins concentration

Increases concentration