Question

What can we get from the electrolysis of NaCl in dissolved state?

Answer 1

Hydrogen gas and chlorine gas

Explanation:

In electrolysis of `NaCl(aq)`, we have `Na^+` and `Cl^-` aqueous ions, and also water molecules `(H_2O)`. When a current passes through, the water molecules also split into `H^+` ions and `OH^-` ions.

Since sodium is more reactive than hydrogen, it would have a higher tendency to stay as an ion, and so hydrogen will get reduced at the cathode, forming hydrogen gas.

The reduction equation for that is:

`2H^++2e^(-)->H_2(g)uarr`

At the anode, chlorine ions get oxidized to form chlorine gas opposed to hydroxide ions `(OH^-)`. That's because the concentration of chlorine ions is greater than the hydroxide ions, and the reduction of `Cl^-` ions is more practical.

The oxidation equation is then:

`2Cl^(-)-2e^(-)->Cl_2(g)uarr`

And then, `OH^-` ions and `Na^+` ions are therefore left in the solution. They combine to make sodium hydroxide `(NaOH)`. This is used to make bleach and many other products.

Together, this is one of the fundamental processes in the chlor-alkali industry, and this process can be called the electrolysis of brine.