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Chemosynthesis
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Quote: Originally posted by Eli25  | by the way where can I find the rightest values of solubility and Ksp?
I want to know if CaSo4 is more insoluble or CaCo3? to know weather adding MgCo3 works better or adding MgSo4 to my solution to gain purer MgCl2!!!!
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If handbooks like CRC, Lange's and Merck don't suit you, consider checking what are known as critical
tables.
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blogfast25
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| Quote: Originally posted by Eli25 | by the way where can I find the rightest values of solubility and Ksp?
I want to know if CaSo4 is more insoluble or CaCo3? to know weather adding MgCo3 works better or adding MgSo4 to my solution to gain purer MgCl2!!!!
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Solubility products:
http://bilbo.chm.uri.edu/CHM112/tables/KspTable.htm
| Quote: Originally posted by DistractionGrating | | Then, there is the "common ion effect" that can make some substances much less soluble when a common cation or anion is present. I'm still trying to
figure this all out myself. |
It is, simply put, the consequence of solubility products:
AB(s) < === > A<sup>+</sup>(aq) + B<sup>-</sup>(aq)
Ks = [A<sup>+</sup>] x [B<sup>-</sup>]
If the solution now also contains A<sup>+</sup>(aq) OR B<sup>-</sup>(aq) coming from another soluble compound, then it will
push the equilibrium further to the left, rendering the compound AB even more insoluble. Example: CaCO3 + K2CO3. Discuss. 
[Edited on 16-5-2015 by blogfast25]
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DistractionGrating
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I have a basic grasp of the common ion effect. The part I'm wrestling with is how, for example, the presence of Mg and/or SO4 can make CaCO3 *more*
soluble, as is the case in seawater.
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blogfast25
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| Quote: Originally posted by DistractionGrating | | I have a basic grasp of the common ion effect. The part I'm wrestling with is how, for example, the presence of Mg and/or SO4 can make CaCO3 *more*
soluble, as is the case in seawater. |
One way the presence of 'spectator ions' can affect solubility is that they influence the so-called ionic strength of a solution. This has in turn an
effect on the activity coefficients of the solvated species.
CaCO3's solubility is also, for obvious reasons, quite pH dependent. Dissolved CO2 also has an effect (formation of bicarbonates).
See Debye - Huckel theory for a better understanding. Oh, and good luck: it's complicated theory and that's one of the reasons we mostly assume the
activity coefficients are one (which is only strictly true in infinite dilutions)
Edit: an interesting study that takes activity coefficients into account in the determination of the solubility product of Malachite, here:
http://www.nrcresearchpress.com/doi/pdf/10.1139/v57-177
[Edited on 16-5-2015 by blogfast25]
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