Where do you acquire Ksp data of ionic compounds (best online)?
What I do basically is search Ksp and open the related hits and copy the listed Ksp data, but values on various sites often contradict one another to
a few orders of magnitude (hence one site may report Ksp of A>B and another report Ksp of B>A) and in the end majority vote decides which is
true and which not
Is there a better method?CharlieA - 21-4-2019 at 16:30
Are sure that all the values you are comparing are reported for the same conditions (temperature, etc.)?fusso - 21-4-2019 at 20:20
i think so, i found them on random sites and they didn't mention conditions.fusso - 21-4-2019 at 22:13
Is accurate Ksp data (@ ambient conditions) not a thing?
[Edited on 190422 by fusso]CharlieA - 22-4-2019 at 16:36
Ok, now I am really confused. How does finding the data from random sites insure that they were all measured under the same conditions? Scientific
integrity demands that the conditions of a measurement be clearly stated, so that others can duplicate the measurements with confidence. When
different results are obtained under apparently the same conditions of measurement, then this is a clue that something is amiss with the measurement
method or the theory. This is how science advances, for the most part, by unexpected results.fusso - 22-4-2019 at 21:24
Yea, im confused too, so I decided to simply request for one here and not care about the details.DraconicAcid - 22-4-2019 at 21:47
Some Ksp values will be measured at standard ionic strength; others will be extrapolated to an ionic strength of zero. Different experiments will
also give different values (have you ever seen a class of first-years trying to calculate the Ka of an acid? They all get different values), and for
the Ksp of some obscure salt, people don't often care enough to devote large quantities of effort to get a precise value.fusso - 22-4-2019 at 22:28
Some Ksp values will be measured at standard ionic strength; others will be extrapolated to an ionic strength of zero. Different experiments will
also give different values (have you ever seen a class of first-years trying to calculate the Ka of an acid? They all get different values), and for
the Ksp of some obscure salt, people don't often care enough to devote large quantities of effort to get a precise value.
How high is the error usually?
PS An example I see is Ksp of Al(OH)3 and Fe(OH)3. One give Al(OH)3 > Fe(OH)3 and another Al(OH)3 < Fe(OH)3. Both compounds are a few OOM apart
in both sites. I also remember Cody'sLab saying Fe(OH)3 > Al(OH)3 so apparently one of the site is wrong.DraconicAcid - 23-4-2019 at 00:22
The hydroxides are complicated also by the formation of complex ions such as [Al(OH)]2+, [Al(OH)2]+ and [Al(OH)4]- (not to mention the possibility of
more clustery polyatomic ions). You can't calculate Ksp directly from the solubility (which makes Ksp less useful for such compounds, and less likely
to be well-studied).fusso - 23-4-2019 at 06:12
So that means the site simply use the solubility to calc the Ksp?DraconicAcid - 23-4-2019 at 07:46
So that means the site simply use the solubility to calc the Ksp?
Unlikely. But they probably took different approaches in correcting or the complications, which gave different results.CharlieA - 23-4-2019 at 16:13
Now I am really confused. What do you mean by Ksp? I thought Ksp meant the solubility equilibrium constant. How do you get aluminum hydroxide and
iron(III)hydroxide mixed together. How about giving us an equation. To me for aluminum hydroxide, Ksp = [Al3+] ([HO-]cubed), where the amounts in [ ]
are concentrations.
Also, when you talk about A>B versus B>A, aren't these just the reciprocal of each other?DraconicAcid - 23-4-2019 at 17:05
Now I am really confused. What do you mean by Ksp? I thought Ksp meant the solubility equilibrium constant. How do you get aluminum hydroxide and
iron(III)hydroxide mixed together. How about giving us an equation. To me for aluminum hydroxide, Ksp = [Al3+] ([HO-]cubed), where the amounts in [ ]
are concentrations.
Also, when you talk about A>B versus B>A, aren't these just the reciprocal of each other?
That is what Ksp means. Nobody said anything about mixing them together.fusso - 23-4-2019 at 21:17
And > means greater than instead of over...maldi-tof - 24-4-2019 at 08:27
I use the data from CRC Handbook of Chemistry and Physics. I suposse it can be "obtainable".
There, if I am not wrong, it is given the article/book where the data come from, if you want to check the experimental conditions.fusso - 24-4-2019 at 08:37
I use the data from CRC Handbook of Chemistry and Physics. I suposse it can be "obtainable".
There, if I am not wrong, it is given the article/book where the data come from, if you want to check the experimental conditions.
Do you have a soft copy of at least the Ksp data of ionics?DraconicAcid - 24-4-2019 at 08:44
My bad. I seem incapable of deciphering ambiguous statements. I don't feel it is my duty to see how many different ways a vague statement can be
interpreted.unionised - 24-4-2019 at 22:29
My bad. I seem incapable of deciphering ambiguous statements. I don't feel it is my duty to see how many different ways a vague statement can be
interpreted.
It wasn't "vague" or "ambiguous"maldi-tof - 25-4-2019 at 10:40
I use the data from CRC Handbook of Chemistry and Physics. I suposse it can be "obtainable".
There, if I am not wrong, it is given the article/book where the data come from, if you want to check the experimental conditions.
Do you have a soft copy of at least the Ksp data of ionics?
I can take pictures of them and make a pdf file. I will take them ASAP, becasue unfortunately, the CRC Handbook is not in my bedside table right now
