Question

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

Answer 1

see below

Explanation:

During electrolysis, at the anode it will form the specie that has the lower redox potential and that need the lower energy.
In a water solution you have as anions and as anodic reactions :
`4OH^- = 4 e + O_2 + 2 H_2O` with
`E = (1,23-0,06 pH) V`
and at pH about 7, E = 0,81 V
and
`2SO_4^(2-)= 2e + S_2O_8^2-` with E= 2,01 V
hence you will have `O_2`