Experiment 7 Determination of the Dissociation Constant of a Weak Acid DONE.docx

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LABORATORY REPORTExperiment 7Determination of the Dissociation Constant of a Weak AcidName:____Emily Jaramillo_______________________Date:__3/22/18___________Lab Partner’s Name:__Ilka Gomez, Hina Shah, Hamza Mirza___Score: ___________I.IntroductionOnce an acid is placed into water it begins to disassociate at a constant rate into its anions andhydronium cations. This is expressed by the equation HA(aq) + H2O(l)A-(aq) + H3O+(aq). Theconcentrations over the reactants of this equation, excluding water (a pure liquid) are used to find the Kaor equilibrium constant of an acid in water:Ka is an intensive property of an acidic compound meaning it does not depend on the amount of theacid compound present. The Ka can thus be used to find an unknown acid compound.A strong acid willcompletely ionize when placed into water, however, a weak acid will only partly ionize leaving manyunreacted molecules in the solution. The two techniques used in this experiment to find the Ka of a weakacid were the titration technique and just measuring the pH of the acid. The purpose of titrating the acidwith a base is to form a pH curve which can then be used to find the half equivalence point where 50%of the acid has been titrated to from A-and 50% remains as HA. From this value we can then find thecorresponding pH. Since pH= pKa we can then calculate Ka by using 10-pKa. The main goal of thisexperiment was to find the Ka of a weak acid using the titration technique and just by measuring the pHso that we can compare which technique is more accurate. During this experiment it was important towear the appropriate PPE in order to shield the skin and eyes from the acid (Acetic Acid) and base(NaOH) used.
II. Results AnalysisA.DataPart I Determination of pKa Using TitrationEquivalence point = 24.36 mLHalf Equivalence point = 12.2 mL

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Term
Fall
Professor
Dr. Wei
Tags
ph curve

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