Determination of the Ionization Constant for a Weak Acid from a Titration Curve.pdf

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Determination of the Ionization Constant for a Weak Acid from a Titration CurveAbstract:The purpose of this laboratory experiment was to determine theof a weak acid fromKaa titration curve. This was done by creating a solution of 20.00 mL of an unknown weak acid andtitrating it with a strong base of 0.1247 M NaOH. The’s determined for Unknown 198 wereKa,. The percent error of the end.193e1−2.802e, 4.449e, 4.923e, 4.635eand5.569e4−2−2−2−2−2point volume and the equivalence point was 0.4317 % while using the Methyl Orange indicator.Method:Laboratory Manual methods were applied. (Diablo Valley College ChemistryDepartment, Fall 2019.) The indicator used was Methyl Orange that has a range of pH 3.1-4.4.Introduction:A weak acid is one that does not completely ionize in solution as strong acids do.If theattraction betweenandis weak, then the acid is strong and vice versa. The strength of aH+Aweak acid is quantified with the acid ionization constant (), also referred to as the equilibriumKaconstant for the ionization reaction of a weak acid.This reaction will yield the followingKaexpression:AH OH OAH(aq)+2(l)3+(aq)+(aq)Ka=[HA][A][H O]3+This lab’s goal was to figure out theof our weak acid in order to identify it. The pHKascale was used in the process as a way to quantify acidity and basicity of a solution.pH = -log[]. In this experiment, a pH meter was used to record the pH as small increments of NaOHOH3+were added to the weak acid. The pH of a solution usually changes greatly if an acid or base isadded, however, a buffer resists pH change by neutralizing any added acid or base. The mainreaction was of an unknown weak acid, HA, that produced its conjugate base,, and thereforeAcreated a buffer that resisted pH change. The strong base of NaOH was added to the solution of20.00 mL of HA and80 mL of, meaning that the acid would neutralize the added base.OH2The HA solution received a few drops of Methyl Orange indicator in order to determine where

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Term
Fall
Professor
DR.GERKEN
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