Experiment 5 Lab Report - Experiment 5 pH Titration...

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Experiment 5: pH Titration: Phosphoric Acid in Cola DrinksIntroductionPhosphoric acid causes a “pleasant tartness” in soft drinks and keeps them carbonated. This experiment explores how the phosphoric acid concentration in a soft drink can be measured using an acid-base titration. The acidity constants for phosphoric acid can also be determined by monitoring changes in pH while titrating. Titration will be conducted using a sodium hydroxide titrant where phosphoric acid is the analyte. In this titration, small amounts of titrant will be added to the analyte until there is a visible change in the solution. This analysis is possible because phosphoric acid is a weak acid. This means that it is only partially ionized (depronated) in an aqueous solution. The equilibrium for this reaction is modeled by the acidity constant, Kawhere .This weak acid is neutralized by being titrated by a strong base. The concentration of the weak acid decreases as the concentration of its conjugate base increases. Monitoring these changes results in a titration (pH) curve. On this curve, the equivalence point I s the point where the number moles of acid is equal to the number of moles of base. This is when the acid has beenneutralized by the base. This is also it is possible to find the concentration of the analyte by only knowing the number of moles of titrant that needed to be added until neutralization.

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