Chem 163 Phosphoric Acid in Cola Winter 2019 DATA Concentration of NaOH (M) ______0.01_______ M H 3 PO 4 Cola Temperature of Analyte at beginning of titration (°C) 21.6 o C 26.1 o C Exact volume of Analyte (before diluting with water) 10.00mL 20.00mL pH of Analyte BEFORE ADDING H 2 O (for K a1 calculation) 2.98 2.74 from your titration curves: Volume of NaOH required to reach 1 st equivalence point 9.25mL 10.0mL Volume of NaOH required to reach 2 nd equivalence point 19.25mL 20.0mL CALCULATIONS Calculate the molarity of the Analyte. Calculate Ka1 based on initial pH and initial [H3PO4]. Calculate Ka1 using pH at the half-equivalence point. Calculate % dissociation of H3PO4 (in initial sample before titration). Calculate %dissociation of H2PO4- (at the 1st equivalence point). Calculate Ka2 For H 3 PO 4 , we are given that the Molarity is 0.01M and we used 10mL, now to find Molarity of the Analyte in Cola, we use M1V1 = M2V2. Therefore M 2 = (9.4*10 -3 ) * (.01)/ (.02) = .01M Cola. This also applies for finding Volume at pH 1/2 Solving for pH based on initial H3PO4 is -log ((10 -5.05 ))
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