Question

How does oxygen form at the anode during the electrolysis of sodium sulfate solution?

Answer 1

Hint: Electrolysis is used in industry for obtaining numerous elements, for example, sodium, aluminum, lithium, chlorine, fluorine and others, and furthermore important substances, for example sodium hydroxide and potassium chlorate. It is utilized for decorative coatings of things, for example with gold or chromium. Electrolysis is also utilized to clean ancient artefacts of nonmetallic impurities, for example coins and blades.

Complete step-by-step answer:
The dissociation of sodium sulfate happens in the water, for example it separates into particles when an electric current is gone through the water, and the particles begin to move. Cations to the cathode, and anions to the anode.

As sodium sulfate is a salt of a reactive metal and an acid containing oxygen, water is subjected to electrolysis with the release of gas hydrogen on the cathode, and oxygen on the anode. Before electrolysis begins, the litmus indicator has a purple color, as the sodium sulfate solution has a neutral medium.

During electrolysis, at the anode, it will frame the species that has the lower redox potential, and that needs the lower energy. In water solution you have anions and anodic reactions:
$$4O{H}^{-}=4e+O_2+2H_{2}O$$ With $$pH=7,E=0.81V$$
And $$2S{O}_4^{2-}=2e+S_2{O}_8^{2-}E=2.01V$$

Hence, we will get oxygen at anode.

Note: Throughout electrolysis, the medium of the electrodes transforms: it becomes alkaline by the cathode and the litmus turns blue, and by the an­ode it becomes acidic and the litmus turns red. In the electrolysis of solutions of salts with particles of metals of medium reactivity – manganese, chromium, zinc, and others the metal and hydrogen will be deposited on the anode. In the electrolysis of solutions of salts of non-reactive metals, for example platinum, mercury and gold, just the metal will be deposited on the anode.