Ok, does anybody else want to play with this?
Quantitative Chemical Analysis 5th Ed. - Harris
has this worked example:
What is the maximum Cl- concentration at equilibrium in a solution in which
[2Hg2+] is somehow FIXED at 1.0E-9 M? Our concentration table looks like
this:
Hg2Cl2(s)<===>Hg(2)2+ + 2Cl-
---------------------------------------------
Initial concentration 0 1.0E-9 0
Final concentration solid 1.0E-9 x
---------------------------------------------
[Hg(2)2+] is not x in this example, so there is no reason to set [Cl-]=2x.
The problem is solved by plugging each concentration into the solubility
product:
[Hg(2)2+][Cl-]^2 = Ksp
(1.0E-9)(x)^2 = 1.2E-18
x = [Cl-] = 3.5E-5 M
Here is my thinking;
For every Ag+ ion released into the water an OH- ion is created (due to the
release of H2 gas) so the [OH-] (concentration) increases at the same rate
as the [Ag+].
Now if [H+] was to remain the same as found in the water (1.0E-7) then using
the template described above (except that x is not squared because there is
only 1 Ag+ in AgOH) the equation looks like this:
[OH-][Ag+] = Ksp
(1.0E-7)[Ag+] = 1.52E-8
[Ag+] = 0.152M or 16,416 mg/L
However, as the amount of OH- rises the solubility of Ag+ falls, but to
counter this effect hydrated Ag+ acts as a Lewis acid forming complex ions
with 4(?) water molecules, and frees some H+ ions into the water and taking
some OH- ions out of the water (so to speak). I'm not sure how to account
for these effects completely, but it seems clear that the solubility of
silver ions, if introduced as ions is far higher than some would
believe....I think they are using an equation that only applies if there is
AgOH solid present in the solution, and the solution is at equilibrium.
Or have I got this completely wrong?
BTW Roger, if you are out there? I think you asked why the colloid becomes
acidic...it is probably due to the Lewis acid effect of transition metals.
Ivan.
--
The silver-list is a moderated forum for discussion of colloidal silver.
To join or quit silver-list or silver-digest send an e-mail message to:
[email protected] -or- [email protected]
with the word subscribe or unsubscribe in the SUBJECT line.
To post, address your message to: [email protected]
Silver-list archive: http://escribe.com/health/thesilverlist/index.html
List maintainer: Mike Devour <[email protected]>
