Can you separate compounds by changing solubility?

  • Thread starter Thread starter Serj
  • Start date Start date
  • Tags Tags
    Solubility
Click For Summary

Discussion Overview

The discussion centers on the separation of soluble compounds by manipulating solubility, particularly through changes in concentration and the common ion effect. Participants explore theoretical scenarios involving compounds like nitrates and their solubility characteristics in aqueous solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question whether soluble compounds can be separated by changing concentration and whether more soluble compounds can push less soluble ones out of solution.
  • Others mention the Solubility Constant (Ksp) and its role in determining the concentrations at which compounds will precipitate, highlighting that differences in Ksp and the presence of common ions are crucial.
  • There is a discussion about the common ion effect, with some participants asserting that adding a common ion can precipitate the less soluble compound, while others express uncertainty about the interactions between different compounds.
  • One participant argues that adding a compound with a common ion would be necessary to achieve precipitation, while another suggests that the less soluble compound would precipitate first when a more soluble compound is added.
  • Concerns are raised about overgeneralizations regarding saturation states, with specific examples of different acids mentioned to illustrate the complexity of solubility dynamics.
  • Participants express interest in finding resources for Ksp values and solubility data.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mechanisms of separation or the implications of solubility changes, with multiple competing views and uncertainties remaining throughout the discussion.

Contextual Notes

Limitations include the dependence on specific conditions such as concentration, temperature, and the presence of other ions, which are not fully explored in the discussion.

Serj
Messages
94
Reaction score
0
Can you separate soluble compounds by changing the concentration? Are some soluble compounds more soluble than others? If you had a nitrate (KNO3, NaNO3, etc) and another less soluble compound in a 1.0M solution in water and you added more and more nitrate compound would the less soluble compound start leaving solution ,get pushed out by the nitrate so to speak, and form a solid precipitate?

Thank you,

-Serj
 
Chemistry news on Phys.org
Ain't sure...
But yes.

Have you come across the Solubility Constant (Ksp)?

Ksp's of soluble compounds tell you what concentration will dissociate (and thus what concentration will remain as a precipitate)

If the Ksp's of the 2 compounds are different AND they share a common ion, then by adding that common ion you can precipitate the less soluble compound. The extent to which you can do this depends on how much of both compounds you've added and how different their Ksp's are.


And although it may be possible to force an unrelated compound out of solution, it's more efficient to use something with a common ion.
 
If the two compounds have any of the same ionic components, then we're talking about the common ion effect.

Note that all compounds have a saturation state in water and furthermore a supersaturation state.

Assuming an very large excess of water, the two compounds will not interact appreciably for any changes in solubility. If someone knows of a specific, interesting dynamic, let me know.
 
Valce said:
Ain't sure...

And although it may be possible to force an unrelated compound out of solution, it's more efficient to use something with a common ion.


Wouldnt the only way to get the common ion be two add one of the compounds sharing the same common ion? If you had CaNO3 and NaNO3 in a solutin and you added more CaNO3, wouldn't you push the NaNO3 out of solution even if NaNO3 is more soluble?
 
No, calcium nitrate will precipitate first.
 
Wouldnt the only way to get the common ion be two add one of the compounds sharing the same common ion? If you had CaNO3 and NaNO3 in a solutin and you added more CaNO3, wouldn't you push the NaNO3 out of solution even if NaNO3 is more soluble?

It's clear that if you add CaN03 to a solution containing NaN03 and the former is less soluble than the latter, the solution will become saturated quickly with respect to CaN03. The CaN03 will simply not dissolve further, since the solution is supersaturated; it will not dissociate to Ca2+ and N032-.

got it?
 
GCT said:
It's clear that if you add CaN03 to a solution containing NaN03 and the former is less soluble than the latter, the solution will become saturated quickly with respect to CaN03. The CaN03 will simply not dissolve further, since the solution is supersaturated; it will not dissociate to Ca2+ and N032-.

got it?



oh, yes that makes more sense now that I think about it. Can you link me to a chart of compounds and their Ksp?
 
Last edited:

Similar threads

  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
6K
Replies
11
Views
5K
  • · Replies 1 ·
Replies
1
Views
10K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
1
Views
6K