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Topic: Concentrations of Multiple Acids  (Read 2402 times)

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Offline ekoez

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Concentrations of Multiple Acids
« on: October 20, 2010, 08:30:41 PM »
If I did a titration with an acidic solution with a base, and the solution was made up of more than one acid (e.g. citric acid and ascorbic acid), would it be possible to determine the individual concentrations of the acids?

I believe that answer is no, but I've also heard about acid strengths and perhaps it is possible to determine the individual concentrations of the acids based on their acid strength?

Thanks for the help.

Offline DemonicAcid

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Re: Concentrations of Multiple Acids
« Reply #1 on: October 20, 2010, 10:39:38 PM »
Think about the chemical reactions involved in the titration. Draw out a rough sketch of what the titration curve will look like. Will you be measuring the pH at every point along the curve or will you only be using an indicator to find the end-point of the titration? Think your problem through.

Offline ekoez

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Re: Concentrations of Multiple Acids
« Reply #2 on: October 20, 2010, 11:14:32 PM »
An indicator will be used.

I'm thinking no because you cannot determine the respective amounts of the different acids even if you have their acid strengths. There could be a lot or a little of every individual acid, but you aren't able to specifically determine their amounts?

Offline Borek

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Re: Concentrations of Multiple Acids
« Reply #3 on: October 21, 2010, 02:53:35 AM »
A lot depends on the relative strengths of the acids. If the differences are high enough, you can see two well developed end points, that can be enough to determine both acids from one titration.

Compare with Warder titration - http://www.titrations.info/acid-base-titration-sodium-hydroxide-and-carbonate - while this is about two bases determined from one sample, idea is the same.

Sometimes it is possible to make the differences between acid strengths larger by correct selection of solvent, you don't have to do water titration.

That said, I doubt any of these will works for the mixture of citric and ascorbic acid.
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