There was a question in our final exam (bachelor's grade) :
""How is the solubility (in water) of AgCl affected by adding :
1. HNO3
2. NaOH ""
I found two different answers to this question (in chem literature).
1 answer - the solubility is not affected in both ways.
2 answer - as AgCl is a salt of weak base (AgOH) and strong acid (HCl) if the pH reises (basic solutin) the solubility increases. Decreasing pH
decreases solubility.
[Edited on 29-7-2006 by simply RED]SHOT - 29-7-2006 at 16:45
I think solubility wont change. AgCl is compleatly not soluble. I think adding HNO3 will make AgNO3 and HCl and adding NaOH will make NaAgO plus HClNerro - 29-7-2006 at 16:59
Adding HNO3 to AgCl does not form HCl and AgNO3 because HCl is a tronger acid than HNO3
I'm not sure about the second one though but it might be true.SHOT - 29-7-2006 at 17:02
My idea is based on reactivity. Ag is more reactive then H so it removes it from h-no3 to give ag-no3 and h-clBromicAcid - 29-7-2006 at 17:41
In my quantitative analysis class we determined the chloride concentration of an unknown by addition of a AgNO3 solution to precipitate silver
chloride and then dried and weighed the product. It had to be washed with dillute nitric acid before it was dried but the teacher warned that washing
too much would dissolve some of our product and affect our yield (of course since this was quantitative chemistry, the yields had to be very precise).
There was a whole chapter though on silver chloride solubility (and the solubility of generally considered insoluble compounds in general) in our
text book (which I actually sold) regarding the AgCl/Ag electrode and more to do with AgCl and solubility perameters. Don't remember too much though.agent_entropy - 29-7-2006 at 20:42
I found this answer at the page linked below (the quoted paragraph is found in the conclusions section). It makes sense to me though I don't have a
copy of the Merck Index (yet) so maybe someone who does could confirm it.
"It is well-known that silver chloride is highly insoluble, even in nitric acid; however, beginning chemistry texts often neglect to mention that
silver chloride will in fact form a soluble complex ion (AgCl2-) in the presence of excess chloride. AgCl is therefore soluble in excess NaCl or
concentrated HCl, especially when some AgNO3 is present (Merck Index, 1983)."
It seems reasonable to me. You might get some increased solubility from the common ion effect too.
[Edited on 30-7-2006 by agent_entropy]guy - 29-7-2006 at 20:47
Quote:
Originally posted by agent_entropy
It seems reasonable to me. You might get some increased solubility from the common ion effect too.
[Edited on 30-7-2006 by agent_entropy]
Common ion effect DECREASES solubilityunionised - 30-7-2006 at 00:22
In the first web page (Q16) it says AgOH is a weak base- I don't think that's true. While the stuff has a rather low solubility, the Ag and OH that do
go into solution are fully dissociated.
Also that entire page makes no mention of activity (rather than concentration) so I think it is aimed at a relatively less educated audience.
The sceond web page won't load for me so I can't comment on it.
The presence of any other ionised species will affect the solubility through the "ionic strength" effect but this has nothing to do with pH.
Nitrate is usually thought of as a poor complexing agent (it's fairly big and has a low charge). so I don't think there will be much of an effect
there.
With lots of conc nitric, the HCl would get oxidised to Cl2 and the Ag would end up in solution as AgNO3- that's not really a pH dependence.
With a high enough concn of NaOH you might get some conversion of AgCl to AgOH (this works with PbCl2 and CuCl)
What someone really needs to do is the experiment to measure the solubilities.simply RED - 30-7-2006 at 01:24
"Silver hydroxide is unstable white, insoluble in water substance. It has basic properties. It is fairly strong base and its salts do not hydrolise."
Found in : Inorganic Chemistry by Dobri Lazarov (University edition)
So, AgOH is not be a weak base after all....
[Edited on 30-7-2006 by simply RED]SHOT - 30-7-2006 at 09:26
simplyRED where are you from, because this book has been written by a bulgarian author and i am bulgariansimply RED - 30-7-2006 at 10:40
I'm from BG too, sended you U2U message not to dilute the thread.
