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Topic: Solubility Equilibrium  (Read 775 times)

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Offline emm316

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Solubility Equilibrium
« on: January 17, 2020, 09:03:18 PM »
If the ion concentration of two ions in a reaction are different how will they reach equilibrium?
like in CaSO4  ::equil:: Ca2+ + SO4 2- if the calcium ion concentration is 0.04M and the sulfate ion concentration is 0.01 M and at equilibrium the ion concentration for both is 4.99x10-3 M how would they both get to the same concentration??

Offline Borek

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Re: Solubility Equilibrium
« Reply #1 on: January 18, 2020, 04:03:19 AM »
at equilibrium the ion concentration for both is 4.99x10-3 M

Not necessarily.

how would they both get to the same concentration??

They won't. Equilibrium doesn't mean "same concentrations". It means "no further changes in concentrations".

Yes, for reactions like dissolution of CaSO4 (or AgCl) you can expect concentrations of both ions to be the same, but that's just because of the reaction stoichiometry. What about dissolution of Ag2S? Ca3(PO4)2?

What will happen in your case is that some CaSO4 will precipitate till concentrations of whatever is left will be described by the solubility product (Ksp) of the compound.
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