solving for pH with diprotic/triprotic acids

by dnt
Tags: acids, solving
dnt is offline
Apr20-06, 11:13 AM
P: 238
i know if you have an acid, say .0001 M HCl, to get the pH you simply take the -log of the acid concentration (which is the same as [H+]), but what if you have a diprotic (H2SO4) or triprotic (H3PO4) you need to multiply the acid contentration by 2 or 3 to get the new H+ concentration BEFORE plugging it into -log[H+]?

and the same goes for pOH? eg. Mg(OH)2 needs to be multiplied by 2?
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siddharth is offline
Apr20-06, 12:22 PM
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Check out these links. They should help in answering your question.
Apr20-06, 01:03 PM
P: n/a
Mg(OH)2 do not completely ionise in water as do for instance NaOH or KOH.

Borek is online now
Apr20-06, 06:22 PM
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solving for pH with diprotic/triprotic acids

Depending on your level of education - you may either calculate pH assuming full dissociation, or you may need to calculate dissociation equilibrium. Check out these links: general method for polyprotic acids and bases pH calculation and simplified method of pH calculation for polyprotic substances.


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