Data • Determine the equivalence point of each acid by using: - pH meter: • HCI – pH=7.00 • CH,COOH - Indicator: the point at which the indicator turns "pink" Calculation of the acid concentration: - [acid]=(VNAOH at equivalence mL · 0.100 M)/10 mL Compare to the accepted concentration of the acids: - HCI: 0.100 M - сн,сOон: 0.100 М Use acid-base titration to determine the concentration of: - A strong acid: HCI 0.100 M NAOH (standardized) •0.100 M HCI 0.100 M Cнзсоон Phenolphthalein is used for endpoint determination - Changes from colourless to pink as a solution becomes more basic • Only need 2-3 drops per titration • pH range: 8.3-10 Procedure - Titration of Acid • Ensure that the initial reading of the burette is recorded and that the pH meter is fully submerged into the acid solution before continuing. • Add NaOH from the burette to the acid solution in portions (total volume added: 2, 4, 6, 7, 7.5, 8, 8.5, 9, 9.2, 9.4, 9.6, 9.8, 10.0, 10.2, 10.4, 10.6, 10.8, 11, 12, 14, 16, 18, 20 mL) making sure to write the exact volume added each time and the corresponding pH when it has stabilized. • Record the initial and final burette volume, the pH, and indicator colour in a table (see below for an example). Initial Final Volume pH Colour of volume (* volume (+ 0.05 mL) added indicator 0.05 mL) (+ ? mL) 2.10 4.20 2.10 Apparatus - Burette 24 10 25 Reading 9.63 ml Reading 24.16 ml Titration I Titration 2 Final Reading (ml) 9.63 + 0.05 24.16 ± 0.05 www.indigo.com Initial Reading (ml) 0.00 + 0.05 0.00 + 0.05 Total Volume (ml) 9.63 + 0.10 24.16 ± 0.10 Acid-Base Titration Strong Acid-Strong Base PH Initial Burette Reading Final Burette Reading Total Volume added (mL) (mL) 0.00 (mL) 0.00 1.89 0.00 1.97 0.00 2.02 2.02 2.09 2.25 4.02 4.02 2.02 4.02 6.02 6.02 2.49 6.02 8.01 8.01 2.97 8.01 9.81 9.81 3.07 9.81 10.02 10.02 3.20 3.65 10.02 10.21 10.21 10.21 10.46 10.46 4.39 10.46 10.76 10.76 6.05 10.76 10.96 10.96 10.72 11.61 11.89 12.01 10.96 11.96 13.86 11.96 11.96 13.86 13.86 15.96 15.96 15.96 17.86 17.86 20.02 17.86 12.12 20.02 -- ---