In my textbook it is given that for electrolysis of dilute sulfuric acid at anode following reactions can occur:

At moderate concentrations

$\ce{2H2O -> O2 + H+ +4 e-}$

And for high concentrations

$\ce{2SO4- -> S2O8^2- +2 e-}$

SRP value for first reaction is less than second and hence the first reaction should take place. But why does that not hold for high concentrations?

  • 1
    $\begingroup$ I was taught that at high concentrations, there are too many sulphate ions surrounding the anode. Hence, they get oxidised even if their SRP values disagree. But, I am not sure if this is correct. $\endgroup$ – Gaurang Tandon Mar 8 '18 at 15:58
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    $\begingroup$ Why anyone would think that "standard" value has importance in highly non-standard environment? $\endgroup$ – Mithoron Mar 8 '18 at 15:59
  • $\begingroup$ Do you mean it becomes kinetically preffered? and we have something like overpotential? $\endgroup$ – Karmanya GB Mar 8 '18 at 16:00
  • $\begingroup$ There's not much water around in conc Sulfuric acid $\endgroup$ – Waylander Mar 8 '18 at 16:01
  • $\begingroup$ Related: chemistry.stackexchange.com/q/75108/5026 $\endgroup$ – Gaurang Tandon Mar 8 '18 at 16:07

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