Sciencemadness Discussion Board

Ferrates vs. perxenates

chornedsnorkack - 14-9-2022 at 01:52

Both ferrates and perxenates are renowned as simple salts which are reasonably stable in alkaline aqueous solutions, but rapidly oxidize water in weak acid already.
Ferrates reduce to Fe(OH)3, perxenates to XeO3.
Ferrates in alkaline condition are stable over +400 C and can be made in liquid saltpetre (which is how they were discovered), as well as, in aqueous alkali, by hypochlorite and hypobromite. Perxenates are formed in aqueous alkali by dismutation of XeO3.

Which of them is the stronger oxidant? At near neutral pH, does perxenate oxidize Fe(OH)3 to ferrate, or vice versa?

Also, while perxenic acid decomposes rapidly in dilute acid solutions, in concentrated acid it is easy to separate XeO4. Whereas I have not heard of successful production of H2FeO4 or FeO3. What are the reaction conditions needed for successful production of XeO4 rather than XeO3 and O2?

PirateDocBrown - 14-9-2022 at 10:11

LOL, if you need homework help, just say so.

ave369 - 9-10-2022 at 10:35

I don't think a home chemist can seriously answer a question about xenon compounds. Xenon chemistry is locked behind a fluorine barrier. You cannot make xenon compounds if you don't have free fluorine. No one has that at home, and no one should.

clearly_not_atara - 9-10-2022 at 10:48

http://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)

BromicAcid - 9-10-2022 at 12:17

One of the Inorganic Syn volumes basically had a hardware store list to make a fluorine generator. I had started purchasing equipment for it before I graduated from college, the real hurdle though was the anhydrous HF to feed it. If I had a source of that or the double-salt I'd have certainly been making it in my back yard. For better or worse - perxenates are awesome compounds, it's a shame that there is really no use for them to drive down the price. I remember when I started working in the professional field feeling the same sadness that perbromates are next to impossible to buy despite there being a known synthesis (although there's no specific utility to them).

wg48temp9 - 10-10-2022 at 02:07

Quote: Originally posted by BromicAcid  
One of the Inorganic Syn volumes basically had a hardware store list to make a fluorine generator. I had started purchasing equipment for it before I graduated from college, the real hurdle though was the anhydrous HF to feed it. If I had a source of that or the double-salt I'd have certainly been making it in my back yard. snip


"a hardware store list to make a fluorine generator" that had me intrigued., so I searched for it and found it: electrolysis of a molten mixture of a double salt of a alkali fluoride/hydrogen fluoride and hydrogen fluoride in a copper apparatus with carbon electrodes.
|See https://sci-hub.se/10.1021/ja01268a031

Hydrogen fluoride can be made by heating a mixture of powdered calcium fluoride and concentrated sulphuric acid.

BromicAcid - 10-10-2022 at 04:02

Simple but probably effective. This was the exact post I was talking about though:

http://www.sciencemadness.org/talk/viewthread.php?tid=2358

Still, @chornedsnorkack, you're not planning on making fluorine are you?

chornedsnorkack - 11-10-2022 at 00:44

Quote: Originally posted by clearly_not_atara  
http://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)

Br2(l) + 2 e− ⇌ 2Br−
1.066
2FeO42− + 5H2O + 6 e− ⇌ Fe2O3(s) + 10 OH−
0.81
O2(g) + 2H2O + 4 e− ⇌ 4OH−(aq)
0.401
[HXeO6]3−+ 5H2O + 8 e− ⇌ Xe(g) + 11 OH−
1.18
[HXeO6]3−+ 2H2O + 2 e− ⇌ [HXeO4]−+ 4 OH−
0.99

Sounds that in basic conditions, neither ferrate nor bromine should oxidize xenon to perxenate. Yet, bromine should oxidize xenate to perxenate.
But this is a question of kinetics, not just equilibrium. Bromine should oxidize oxygen, not just ferrate. Ferrate should oxidize oxygen even in basic solution, yet it does not.
What is the kinetics of ferrate oxidation of oxygen in neutral aqueous solutions like?
And I am very aware that not only fluorine but HF are very dangerous stuff far out of actual amateur experimentation league.

yobbo II - 11-10-2022 at 12:41

http://www.sciencemadness.org/talk/viewthread.php?tid=17233#...

and

http://www.sciencemadness.org/talk/viewthread.php?tid=144#pi...

Yob

chornedsnorkack - 2-11-2022 at 23:33

Hypochlorite is quoted as oxidant oxidizing iron to ferrates. Does iron readily dissolve in bleach?
Fe+3NaClO+2NaOH=Na2FeO4+3NaCl+H2O

Bedlasky - 3-11-2022 at 23:27

I think this would be very slow reaction. But maybe I am wrong. Ferrates are usually prepared from ferrous or ferric salts. You could try it. Add in to the test tube small amount of iron with high surface area (powder, steel wool) and add some bleach. It sounds like an interesting experiment.

[Edited on 4-11-2022 by Bedlasky]