Q.Describe, with equations, the industrial preparation of hydrogen peroxide by

1. Electrolytic oxidation of bisulfate. A cold, concentrated solution of ammonium bisulfate (or sulfuric acid) is electrolysed using platinum electrodes. At the anode, the bisulfate ion is oxidised to peroxodisulfate:

   $2\text{HSO}_4^{-} \longrightarrow \text{S}_2\text{O}_8^{2-} + 2\text{H}^{+} + 2e^{-}$

   The peroxodisulfuric acid/peroxodisulfate so formed is then hydrolysed -- carried out under reduced pressure, by distillation, to avoid decomposing the hydrogen peroxide product as soon as it forms:

   $\text{S}_2\text{O}_8^{2-} + 2\text{H}_2\text{O} \longrightarrow 2\text{HSO}_4^{-} + \text{H}_2\text{O}_2$

   The regenerated bisulfate can, in principle, be recycled back to the electrolytic step.
2. Auto-oxidation of 2-ethylanthraquinol (the anthraquinone process). A solution of 2-ethylanthraquinol in a suitable organic solvent is agitated with a stream of air (or oxygen). The quinol is oxidised by the atmospheric oxygen to 2-ethylanthraquinone, and hydrogen peroxide is liberated into the solution in the same step:

   $\text{2-ethylanthraquinol} + \text{O}_2 \longrightarrow \text{2-ethylanthraquinone} + \text{H}_2\text{O}_2$

   The hydrogen peroxide is then extracted from the solvent, and the 2-ethylanthraquinone left behind is catalytically reduced (using hydrogen gas over a palladium or nickel catalyst) back to the original 2-ethylanthraquinol, regenerating the starting material so the whole process can be run as a continuous cycle. This anthraquinone process is the dominant industrial route to hydrogen peroxide today.
   ✓Final answer

   1. $2\text{HSO}_4^{-} \rightarrow \text{S}_2\text{O}_8^{2-} + 2\text{H}^{+} + 2e^{-}$ at the anode, then $\text{S}_2\text{O}_8^{2-} + 2\text{H}_2\text{O} \rightarrow 2\text{HSO}_4^{-} + \text{H}_2\text{O}_2$ on hydrolysis.
   2. 2-ethylanthraquinol is oxidised by air/O2 to 2-ethylanthraquinone while liberating $\text{H}_2\text{O}_2$; the quinone is then reduced back (H2/catalyst) to the quinol, so the cycle repeats continuously.

Recall the two named industrial routes and write out their key steps: the electrolytic route's anodic oxidation + hydrolysis, and the anthraquinone route's air-oxidation + catalytic-reduction regeneration cycle.

Confusing the electrolytic route's peroxodisulfate intermediate with H2O2 itself (the peroxodisulfate must still be hydrolysed); forgetting that the anthraquinone process is cyclic/regenerative, not a one-shot reaction.