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Topic: pH prediction  (Read 1878 times)

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Offline tamubsa

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pH prediction
« on: May 02, 2014, 01:33:50 AM »
If you mix equal amounts of acetic acid and sodium sulfite, will the solution be acidic, basic, or neutral? I would normally go about this by deciding the strengths of the substances that are being mixed, but it seems like we are mixing a weak acid with a basic salt. Would you compare Ka and Kb values?
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Offline Borek

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Re: pH prediction
« Reply #1 on: May 02, 2014, 03:57:38 AM »
No way to approach it without knowing exact pKa values.

Equal amounts like in equal masses, or equal number of moles?
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Offline tamubsa

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Re: pH prediction
« Reply #2 on: May 02, 2014, 12:17:48 PM »
Equal number of moles.
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Offline Big-Daddy

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Re: pH prediction
« Reply #3 on: May 02, 2014, 02:10:59 PM »
If Kb(SO32-)>Ka(CH3COOH) then it's basic, if Ka(CH3COOH)≈Kb(SO32-) then it's also basic but very little (since now we'd be relying on the second association, that of hydrogensulfite, to provide the difference) and if Kb(SO32-)<Ka(CH3COOH) by a significant amount then it's acidic.
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