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Topic: amount of protonated species from pKa and pH  (Read 2647 times)

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Offline zoork34

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amount of protonated species from pKa and pH
« on: November 17, 2006, 05:53:01 PM »
Ok, if i have a .1 M solution of a compound, say, diethylamine, with pKa of about 11, and i put it in water and raise the pH up and down, is there any way i can say exactly how much DEA i have at each pH?  i know from the henderson-hasselbalch equation i can get the ratio of protonated to non-protonated, but i dont know how to get the actual amounts. 

Offline Borek

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Re: amount of protonated species from pKa and pH
« Reply #1 on: November 17, 2006, 05:59:13 PM »
http://www.chembuddy.com/?left=pH-calculation&right=pH-polyprotic-acid-base

See equations 9.11, 9.12 & 9.13 for a hint.

Note: if you have a single proton acid/base, you can use Ka (Kb) definition and [HA] + [A-] = Ca (mass balance) to setup system of two equations in two unknowns - once solved it will give you needed answer.
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