Condition of disharge sulfat anions on anode

[Nimmull]

If sulfat anions discharge on anode in sulfuric acid
producing persulfuric anions (S₂O₈)₂-. But if this happens in melted sulfate producing SO₃ and O or SO₂ and O₂. Why? What conditions effect on this processes? 100% sulfuric acid is not conducting current but if in 100% acid soluble the sulfate (example Al₂(SO₄)₃) then this liquid will conduct current. And what we get in anode space in this liquid? (S₂O₈)₂- or SO₃ + O?

[Nimmull]

Af anybody know books about this thematic please give a links.

[ChenBeier]

No

In diluted sulfuric acid or solution of sulfate salts, SO₄ 2- will be not discharged, instead of Oxygen will be developed.
2 H₂O + 2 SO₄ 2- => 2 H₂SO₄ + O₂ + 4e-

In molten alkalisulfates peroxodisulfate will be created. Technical method to produce persulfates

2 SO₄ 2- => S₂O₈ + 2 e-

https://en.m.wikipedia.org/wiki/Sodium_persulfate

If heavy metal sulfates are used they get decomposed to sulfuroxide, oxygen and remaning oxides.

[Nimmull]

Heavy metal like a iron?

[ChenBeier]

Correct.

[Nimmull]

100% H₂S04 have no water and electrolytic creating the oxygen by discharge OH- anions is impossible this liquid have no OH- anions and have no H₂O. It's a pure sulfuric acid.

[ChenBeier]

Sulfate of Sulfuric acid will convert to peroxodisulfate, further to disulfate and sulfurtrioxide.

2 SO₄ 2-=> S₂O₈ 2- + 2 e-

2 S₂O₈ 2- => 2 S₂O₇ 2- + O₂

S₂O₇ 2- => SO₄ 2- + SO₃

[Nimmull]

If i make electrolysis melted NaHSO₄ what i get Na₂S₂O₈ or SO₃ + O?

[Nimmull]

Sulfate of Sulfuric acid will convert to peroxodisulfate.

2 SO₄ 2-=> S₂O₈ 2- + 2 e-

But where this happened? In liqud sulfuric acid or in melted sulfate? Why peroxidsulfate not created in melted sulfates because high temperature? Peroxidsulfat anions will destroing by temperature or what?

[ChenBeier]

Water free sulfuric acid is like a melted sulfate. Alkalisulfates will stop at Peroxodisulfate, iron, chromium and others decompose to sulfuroxides.

[Nimmull]

But water free sulfuric acid not conducting current (because H₂SO₄ molecule is associated). But if i soluble sulfate in water free sulfuric acid i get current conducting liquid. The question what i get on anode when will do electrolisis in this liquid?

[ChenBeier]

Conc. sulfuric acid has an conductivity of 1,044 · 10−2 S/cm.

It has an autoprotolysis like water

2 H₂SO₄ => H₃SO₄+ + HSO₄-

A sulfate salt enhance because more HSO₄- is produced

H₂SO₄ + Na₂SO₄ => 2 NaHSO₄

[Nimmull]

Ok! But how about anode processes in this liquid ( H₂SO₄ + Na₂SO₄ without water)?

[ChenBeier]

That I wrote above already

[Nimmull]

Ok. If we will do electrolisis of melted NH₄HSO₄ (easy melting just 150°C) what we will get SO₃ + O or (NH₄)₂S₂O₈?