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Old Mar 22nd 2017, 03:16 PM   #1
yona
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Unhappy Fehling titration

Hello.

For my chemistry class, I made simple beer out of malted grains that I heated then cooled.
I want to measure the sugar content of my beer with Fehling titration.

Different types of sugars can be found in beer, such as maltose, which contain an aldehyde (RCHO) function, therefore, the Fehling test can be used.

The sugar will reduce the ions Cu2+ into Cu+ under basic conditions with this equation:

RCOH (aq) + 2 Cu2+ (aq) + 5 OH-(aq) → RCOO- (aq) + Cu2O(s) + 3 H2O (l)

And this is where I get stuck.
Let's say I decide to use 20 mL of beer and that I know the molarity of my Fehling solutions, how could I calculate the volume needed to reach the equivalence point? How can I know what volume of Fehling I should use before I titrate with a sugar sample like dextrose?

Any help is welcome. Thank you very much!
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Old Mar 30th 2017, 04:33 AM   #2
MatthijsM
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you can't, if you have no clue on how much sugar there is in the beer. Perhabs you could do a test titration to look on how much volume you kinda need. So you can adjust your molarity of the fehling solutions
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