AgOH versus Ag2O

[Ferdinand]

For Beau,

 

"My problem is with the

>reaction of ammonia solution and silver as both as ion or solid. In

>particular I would like to know whether AgOH is possible from the

>reaction of limited ammonia solution (being a base) and either

>silver ion or solid. I have searched on the internet for AgOH with

>no result therefore I thought that when silver is reacted with any

>base it either forms a Ag20 precipitate or a Ag(OH)2- ion. I'm also

>not sure which one would be the product from limited ammonia. I

>understand that in excess ammonia silver will form a complex ammonia

>ion but dont know the limited solution. If the product is Ag2O can

>you include the reaction because I'm not sure if 2Ag + OH- --> 2Ag2O

>+ H+ seems quite right. Please can you help me with my query.

>Althought this is not likely to be in the exams it is still

>annoying me."

 

Colleagues, I seek an elegant answer here.

 

Thanks

 

Ferdinand

[dttom]

well, on my view, AgOH should be too unstable to exist, as Ag+ is small and have a relatively high electronegativity, the hydroxide ion if bounded to it would be distorted so that the 'hydroxide' is no longer hydroxide, instead of an oxide is formed, Ag2O. I think the equation should be:

2Ag+ + 2OH- --> Ag2O + H2O

[woelen]

The situation with silver ions is somewhat complicated. When silver comes in contact with hydroxide (from ammonia, or from NaOH-solution does not matter) and no complexing agent is available, then something is formed, which sometimes is referred to as AgOH. This is not correct. But Ag2O also is not correct. Ag2O is a black solid, when silver (I) is added to hydroxide, then a fairly light brown solid is formed. What happens is that an hydrated form of silver oxide is formed, so a better formula is Ag2O.xH2O, but the real structure of the compound is very complicated. It really is another compound than Ag2O, but it also certainly cannot be written correctly as AgOH. I think, in reality, it will be a complex structure with indeterminate stoichiometry, containg Ag(+) ions, OH(-) ions, O(2-) ions and water molecules, and the only thing which can be said is that it has average formula Ag2O.xH2O.

[vknn]

This is maybe the most epic thread resurrection ever, but for those interested in colloidal silver i thought i would chip in. I found this formula could be what you are looking for?

 

2 Ag + 2 OH -> Ag2(OH)2 (silver hydroxide)

 

Ag2(OH)2 <–> Ag2O + H2O (silver hydroxide <-> silver oxide) "colloidal silveroxide"

 

The ionic portion of colloidal silver is a mixture of silver hydroxide and silver oxide, each with a solubility of just over 13 ppm.

 

To get colloidal silver and not colloidal silveroxide we need to boil the silver oxide to get:

 

Ag2O -> 2 Ag + O (silver) "colloidal silver"

 

(I could be wrong here, i just pulled this off the net but it looks decent to me. I also did a test with what is commonly known as colloidal silver by boiling it for 10 minutes, and it indeed turned color just as i had read it should when turning into the claimed proper colloidal silver.)

Edited July 29, 2012 by vknn