35 Phosphoric Acid.doc - Experiment Determining the...

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Chemistry with Calculators35 - 1Experiment35Determining the Phosphoric AcidContent in Soft DrinksPhosphoric acid is one of several weak acids that exist in carbonated beverages. It is a component of all cola soft drinks. Phosphoric acid has a much higher concentration than other acids in a container of soft drink, so its concentration can be determined by a simple acid-base titration.In this experiment, you will titrate a sample of a cola soft drink with sodium hydroxide solution and determine the concentration of phosphoric acid, H3PO4. Hydrogen ions from the first dissociation of phosphoric acid react with hydroxide ions from the NaOH in a one-to-one ratio inthe overall reaction:H3PO4(aq) + OH(aq)  H2O(l) + H2PO4(aq)In this experiment, you will use a pH Sensor to monitor pH as you titrate. The region of most rapid pH change will then be used to determine the equivalence point. The volume of NaOH titrant used at the equivalence point will be used to determine the molarity of the H3PO4.MATERIALSLabPro or CBL 2 interface50-mL buretTI Graphing Calculator100-mL graduated cylinderDataMate program250-mL beakerpH Sensorring standvarious cola soft drinks, decarbonatedutility clamp0.050 M NaOHmagnetic stirrer (if available) distilled waterstirring barPROCEDURE1.Obtain and wear goggles.

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