11/2/20111Strength of Vinegar by AcidAcid-Base TitrationBase TitrationFinal Exercise Final Exercise – 105 points105 points1Last Update: 11/2/2011 11:35 AMConcepts:Strong/Weak AcidsAcid Dissociation/KaConcentrationEnd point / Equivalence pointTitration curvesLogarithmsIndicatorMole Relationships pH & pKaTitrationTechniques:Primary StandardThis weekTitrationpH MeasurementApparatus:BuretspH MeterWeighing by DifferencePreparing precise solutionsStandardizationVolumetric FlaskAnalytical BalancePipet2Last exercise involved acid-base titration in which concentration of NaOH was given.In this exercise, you STANDARDIZEthe NaOH.StandardizationAnalytical determination of purity or concentration of substance through reaction with substance of verifiedpotassium hydrogen phthalate (KHPKHP)composition and purity(Primary Standard)This STANDARDIZATIONinvolves reaction of NaOH with a PRIMARY STANDARD,the weak acid: OOHOO-3K+KHPis a monoprotic weak acid. One available proton.HC8H4O4-+ OH-C8H4O4=+ H2O + [K+]The stoichiometry of the reaction is:1 mol KHP1 mol NaOHSTOICHIOMETRYpKais is 5.45.4Acetic acid, CH3COOH, is also a monoprotic weak acid. 1 mol CH3COOH 1 mol NaOHCH3COOH+ OH-CH3COO-+ H2OIt’s pKais 4.74HpKa= 4.7pH ~ 8.5pHmL of NaOH addedpKa5It does not matter in which order youA.) Standardize NaOH, B.) Titrate UnknownC.) Determine pH of unknownPROCEDUREA. STANDARDIZATIONPrepare solution of known concentration of primary standard, KHP•Weigh sample BY DIFFERENCE*•Dissolve fully in ERLENMEYER•Bring to total volume in VOLUMETRIC FLASK**Must transfer ALLthe solution*Web supplement****Follow manual procedureFollow manual procedure6
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