Turner
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Salt precipitation -- double exchange
I have been wondering this:
Let's say you add a solution of barium nitrate (soluble salt) to a solution of ammonium sulfate (soluble salt).
Really you are adding Barium ions and Nitrate ions to ammonium ions and sulfate ions. I understand that barium sulfate will precipitate, but why?
Shouldn't you just have a solution of these four ions? Or can barium ions just simply not exhist in a solution with sulfate ions?
Also too much I see HCl + NaNO3 ---> HNO3 + NaCl
But adding sodium nitrate to aqueous HCl, you would just be left a solution of H3O+ and Cl- and NO3- and Na+.
So, shouldn't you have equal HCl and HNO3 and NaCl all in solution? I understand that Nitric acid forms in this situation, but no more so than HCl
right? What if you said:
HNO3 + NaCl --> HCl + NaNO3
You would end up with the exact same solution, 4 different free ions all in stoichiometric amounts.
Do I have this right?
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elementcollector1
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1. Check the solubility of barium sulfate, compare to solubility of barium nitrate and ammonium sulfate. Precipitation drives the reaction forwards.
2. I'm not entirely sure, but compare the solubility of sodium nitrate to sodium chloride.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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jock88
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Mutual solubility is the subject.
If any ion pair that 'is floating around' in the solution can form an insoluble compound then that compound will immediately precipitate.
If you add a solution of something-sulphate to a solution of Lead Nitrate you will always immediately get a ppt of Lead Sulphate with something
nitrate staying in solution.
When all combinations of ions could form compounds that are somewhat soluble then things are a bit more complicated as to what willl come out of
solution and when.
See attachement.
Attachment: b_fitch.pdf (300kB)
This file has been downloaded 445 times
Attachment: mut_sol.zip (279kB)
This file has been downloaded 269 times
[Edited on 26-2-2014 by jock88]
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