carbonate titration help

[che100]

i have no idea of how to solve this problem

i have got a 0.082M HCL and i titrated with it 25ml of coca cola in 6ml of 0.980945M NaOH. its a back titration procedure, and i got the following titration curve. the question is that i have to find the concentration of CO2 in the coca cola can.

anyone plz help!

 

and one more thing, in the same experiment, we did another titration for an unknown carbonate solution (possibly Na2CO3). we used the same HCL solution to titrate 25ml of the cabonate solution, and the titration curve is attached. we have to determine the concentration of carbonate in the solution, and i again have no idea. please help i have to submit the paper on tuesday

thx

exp 3.pdf

[dttom]

as for your titration of mixture of coca cola and sodium hydroxide against hydrochloric acid, do you assume the coca cola contains only carbonic acid regarding the reaction involved? as there might be trace amount of other substances such as citric acid and phosphoric acid which may disturb.

[John Cuthber]

Looking at that curve I'd say it's clear that you have several acids present. What you need to do is work out which kink in the pH/ volume curve happens at the right pH to be carbonate rather than phosphate or citrate (or whatever)