June 15, 2021, 12:38:08 AM
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Topic: ACID CONCENTRATION  (Read 322 times)

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Offline EQUATION

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ACID CONCENTRATION
« on: April 13, 2021, 03:05:20 PM »
How can I calculate the concentration of glycolic acid in a mixture of glycolic acid and sulfuric acid. Thank you

Offline Orcio_Dojek

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Re: ACID CONCENTRATION
« Reply #1 on: April 13, 2021, 03:48:23 PM »
You can titrate mixture with NaOH and measure pH.

NaOH reacts first with H2SO4, then HO-CH2-COOH.

You can plot a graph - change of pH vs. volume of NaOH added, there should be two apparent points (first for H2SO4, second for glycolic acid).

Offline Babcock_Hall

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Re: ACID CONCENTRATION
« Reply #2 on: April 13, 2021, 05:37:06 PM »
Equation,

According to the Forum Rules (see red link) you should provide your attempts to answer before we can help you.

Offline EQUATION

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Re: ACID CONCENTRATION
« Reply #3 on: April 14, 2021, 04:01:08 PM »
STEP 1 (A)
20 ml of the mixture sample + 50ml DI water + 50ml sodium fluoride + 2 -3 drops phenolphthalein indicator, + 20 ml ( .05M) sodium periodate + 2 g KI + 20ml (20%v/v) HCl. Then, I titrated with sodium thiosulfate solution until a straw yellow color appeared.  I added 4 ml of starch indicator to the resulting solution and continue to titrate slowly until the blue color disappeared( my endpoint).
STEP 2
I Repeated the same steps as A without sodium periodate. ( I expect to have  a higher value than A, but i got thesame endpoint.

Offline Borek

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Re: ACID CONCENTRATION
« Reply #4 on: April 14, 2021, 05:17:19 PM »
As with every titration the starting point should be the reaction equation, as it is just about following stoichiometry.

Description suggests it is an iodometric method, with back titration of the excess iodine, but I have no idea how the glycolic acid reacts with iodine (and somehow I don't expect the reaction to be entirely stoichiometric)  :o
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline EQUATION

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Re: ACID CONCENTRATION
« Reply #5 on: April 15, 2021, 08:33:33 AM »
@Borek. Thank you for your time.  Please is there a better method you think this can be done?

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