Sciencemadness Discussion Board

AgOH

ChemistryForever - 12-1-2019 at 12:58

Is there any way you can synthesize silver hydroxide ? If you mix AgNO3 with NaOH it will give just Ag2O. Or silver hydroxide does not exist ?

CharlieA - 12-1-2019 at 16:29

https://en.wikipedia.org/wiki/Silver_oxide#Preparation

Did you do any search for information? I think the above article should answer your question.

Tsjerk - 13-1-2019 at 12:57

Apparently Ag2O is a bit soluble in water and forms a silver hydroxide solution.

Ag2O + H2O <-----> 2Ag+ + 2 OH-
With a log Ksp of about -7.7, that would be about 0.2mM, so you can make a solution of it at least...

CharlieA - 13-1-2019 at 17:52

According to the Wikipedia reference in my post above, the Ksp for AgOH is 1.52E-8 mol/L. From this value I calculate the solubility of AgOH at 1.2E-4 M or about 150mg AgOH per liter. I wouldn't consider this substance even sparingly soluble in water. But this is just my interpretation, and as they say "it's all relative.":D

P.S. For the newbies, 1.52E-8 is exponential notation and is a shorthand way to express the number 1.52 times 10 to the -8 power.

Edited by Charlie to remove the unintelligiblity of the original post. I'm typing from a laptop and I have the annoyin habit of touching the touchpad while typing, and the &*&*&*& cursor jumps all over the place, so the text that I am typing winds up all over the place. Besides this problem I also write run-over sentences.:D
Charlie



[Edited on 1-15-2019 by CharlieA]

SelfInflicted - 13-1-2019 at 20:30

The hydroxide AgOH exists only in solution; otherwise it spontaneously decomposes to the oxide.

According to https://en.m.wikipedia.org/wiki/Silver

Tsjerk - 13-1-2019 at 23:34

Quote: Originally posted by CharlieA  
According to the Wikipedia reference in my post above, the Ksp for AgOH is 1.52E-8 mol/L. From this value I calculate th1ess I wouldn't consider this substance even sparingly soluble in water. But this is just my interpretation, and as they say "it's all relative.":D


Maybe the wiki concentration is for alkaline solutions? Although silver mainly exists as AgO- in alkaline solution.

Here is an experimental article on the subject.


Attachment: johnston1933.pdf (956kB)
This file has been downloaded 475 times

CharlieA - 14-1-2019 at 16:27

@Tsjerk: thanks for the copy of that article (it's even older than me). I am enjoying reading it and puzzling it out.
Charlie

Edit: ...it's even older than I (am old)...

[Edited on 1-15-2019 by CharlieA]

chemister2015 - 4-2-2019 at 02:07

Silver hydroxide can be obtained at -50 ° C by pouring out alcoholic solutions of silver nitrate and potassium hydroxide.

AJKOER - 4-2-2019 at 17:15

Interestingly, the limited solubility of Ag2O producing AgOH is not necessarily limiting!

In the following system:

Ag2O + H2O <---> 2 AgOH

2 AgOH + 2 Cl- --> 2 AgCl (s) + 2 OH-
------------------------------------------------------

Net: Ag2O + H2O + 2 Cl- --> 2 AgCl (s) + 2 OH-

So adding KCl to a suspension of Ag2O in water can result in strong KOH (capable of attacking glass, as I discovered accidentally) as the formation of the insoluble AgCl apparently drives the first equilibrium reaction to the right.

An extract of my prior comment:
Quote: Originally posted by AJKOER  
OK, a few comments.

I did not dream of the Ag2O route as a path to conc NaOH or KOH (and relatively pure product as well), I accidentally observed it when it ate my glassware (so more like a real nightmare) and reported it on SM (see comments and links at http://www.sciencemadness.org/talk/viewthread.php?tid=69061#... )!
......................

[Edited on 3-1-2019 by AJKOER]


Link: http://www.sciencemadness.org/talk/viewthread.php?tid=117891

[Edited on 5-2-2019 by AJKOER]

Sulaiman - 4-2-2019 at 17:56

would this reaction not occur ?
4AgCl + 4KOH «→» 4KCl + 4Ag + O2 + 2H2O
which would consume the KOH

Tsjerk - 5-2-2019 at 00:21

@ AJOEKER; Just read the abstract.

Attachment: willbanks1953.pdf (706kB)
This file has been downloaded 352 times

@ Sulaiman; not in water. The reaction you propose is driven to the right because of the precipitation of Ag2O. The product van be decomposed by heat, but the equilibrium you wrote doesn't make sense as it implies silver making its way back to the chloride. As a total scheme of two reactions your scheme is correct though.


[Edited on 5-2-2019 by Tsjerk]