bolbol
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Sodium Sulfate unusual solubility
I have been recently working on producing sodium sulfate crystals from saline lake waters. I was browsing on wikipedia when I found that the
solubility increases tenfold at around 32 degrees celsius because thats the melting point of sodium sulfate decahydrate. I was blown away by this but
couldnt find more information on this so I thought I'd ask here.
So if you have a salt solution what is different in the chemistry of bonding if the solutes are past their melting point?
Say we have a solution of a certain salt at 10 degrees Celsius. The salt by itself would be solid at room temperature. Say that same salt would be in
liquid form by itself at a temperature of 40 degrees Celsius. If you bring the solution of that salt with water from 10 degrees C to 40 degrees C is
there really any change? Because dissolved ions are dissolved ions in my mind and I can't see what would be different if they are past their melting
point or not.. I just assume each ion is surrounded by a hydration sphere.
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Σldritch
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Perhaps the innermost solvation shell stays the same with most sodium ions. It is after all the one that should be bonded the tightest to the ions. In
Sodium Sulfate's case it should be five per sodium ion, one less than what can be coordinated to it. In the solid decahydrate, it could be that the
last two electrons in the sodium ion's shell is filled by the sulfate ion.
Also note that the rapid solubility increase is also due to the release of water from the hydrate forming a lower melting point mixture of water,
decahydrate and lower hydrates.
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bolbol
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Quote: Originally posted by Σldritch  | Perhaps the innermost solvation shell stays the same with most sodium ions. It is after all the one that should be bonded the tightest to the ions. In
Sodium Sulfate's case it should be five per sodium ion, one less than what can be coordinated to it. In the solid decahydrate, it could be that the
last two electrons in the sodium ion's shell is filled by the sulfate ion.
Also note that the rapid solubility increase is also due to the release of water from the hydrate forming a lower melting point mixture of water,
decahydrate and lower hydrates. |
Excuse my ignorance but I do not understand the part about the release of water. When I think of a hydrate mineral, I can only imagine it in its solid
form. When its dissolved I imagine it as a mixture of Na+, NaSO4-, Na2SO4, and SO4 2- ions moving around in the solution of water. How can the
dissolved species be hydrated in the first place to be able to then release the water? How can the solution have a dissolved hydrate mineral?
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CharlieA
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Maybe this will help.
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclatu
re_of_Coordination_Compounds/Ligands
Also, I don't know of any evidence for the species NaSO4-; do you have a reference to this?
Thanks, Charlie
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fusso
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| Quote: Originally posted by CharlieA | Maybe this will help.
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclatu
re_of_Coordination_Compounds/Ligands
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| Quote: | | Sorry, the page at
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclatu
_re_of_Coordination_Compounds/Ligands could not be found. |
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DraconicAcid
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| Quote: Originally posted by fusso | | Quote: Originally posted by CharlieA | Maybe this will help.
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclatu
re_of_Coordination_Compounds/Ligands
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| Quote: | | Sorry, the page at
https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclatu
_re_of_Coordination_Compounds/Ligands could not be found. |
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Take out the extra bit in the middle of the word "Nomenclature"
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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bolbol
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Okay so, at the temperature around 30 C, the dissolved species with 10 water molecules as ligands dehydrate. Meaning they are more stable with less
ligands of water molecules around them?
Also, I don't have a reference for speciation of sodium sulfate in water but I am assuming all of those are present at some concentration. The
dominant ones being Na+ and SO42-
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