Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: lily1998 on April 10, 2016, 09:27:57 AM
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Hi,
I am thinking of doing an investigation on the amount of phosphoric acid in coca-cola (coke). Assuming that it contains only carbonated water and phosphoric acid in which sugar, caffeine and other flavorings are in solution, can use I back titration to find out the amount of phosphoric acid? That is using a pH probe to monitor the titration and initial heating of the coke to remove the carbonated water.
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What alkalis/bases/chemicals are you going to titrate with?
And, just curious, why do you need to use back titration?
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I plan to titrate it with NaOH. Sorry about that i meant to say back titration if i used a weak base. But since i am using a strong base it will be direct titration. But is my overall procedure correct?
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Do you think that the other ingredients will have an effect on your results?
https://en.wikipedia.org/wiki/Coca-Cola_formula (https://en.wikipedia.org/wiki/Coca-Cola_formula)
https://en.wikipedia.org/wiki/Confounding (https://en.wikipedia.org/wiki/Confounding)
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Which indicator you are planning to use?
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That is using a pH probe to monitor the titration and initial heating of the coke to remove the carbonated water.
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You could measure titratable acidity (TA) of the Coca Cola after you let it go flat (most carbon dioxide escapes therefore negligible carbonic acid in solution) then remaining acidity will be due to phosphoric acid. By measuring TA when fresh soft drink is first opened and subtracting this value from above value, you can approximate the carbonic acid contribution to TA. I am not sure how a colour indicator will allow visualization of the endpoint due to the caramel colouring in Coca Cola, so an endpoint determined by electrical conductivity would be ideal (ie. Karl Fischer Titrator, etc.)