potentiometric (15).docx

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UNIVERSITY OF BALAMAND Faculty of Sciences Department of Chemistry Basic Chemistry Laboratory Names: Lara Frangieh ID: A0810408 Anthony Dahdah ID: A0810784 Experiment Title: Acid-Base Potentiometric (pH) Titration Experiment Week: Week 7 Date: 19/11/09 Submitted to: Dr. Robin Taleb 1
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Introduction: A titration is a laboratory process for quantitative study. In a titration two reagents are mixed. Every titration has a curve: the curve obtained with a strong acid, weak acid, and a polyprotic acid. The polyprotic acid is neutralized in three steps with a strong base (NaOH) while a strong acid is neutralized in one step. The phosphoric acid ( H 3 PO 4 ) is a polyprotic acid, and the hydrochloric acid is a strong acid (HCl). The phosphoric acid could be found in many cola drinks. In this experiment, pH-meter was used instead of colorimetric indicators. The aims of the experiment were: To plot the titration curve of pH vs. volume of NaOH, and determine graphically the equivalence point (experiment 10.1) To plot the titration curve as pH vs. ml of NaOH, and to determine the molarity of the phosphoric acid and graphically the values of pKa 1 and pKa 2 (experiment 10.3) To plot the graph of pH vs. volume of NaOH, and to determine the molarity of the phosphoric acid in the cola drink (experiment 10.5) Reactions: Experiment 10.1: 1. HCl + NaOH NaCl + H 2 O 2
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Experiment 10.3/5: 2. H 3 PO 4 + NaOH NaH 2 PO 4 + H 2 O 3. NaH 2 PO 4 + NaOH Na 2 HPO 4 + H 2 O 4. Na 2 HPO 4 + NaOH Na 3 P O 4 + H 2 O 5. H 3 PO 4 + 3NaOH Na 3 PO 4 + 3 H 2 O Used equipments: 250 ml beaker 10, 25, 50 ml pipette pH-meter burette magnetic stirrer heating mantle Used chemicals: Hydrochloric acid solution HCl (0.1M) Sodium hydroxide solution NaOH (0.05, 0.1M) Unknown phosphoric acid solution H 3 PO 4 Cola drink Distilled water Method: Experiment 10.1: 3
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Using a 10 ml pipette, the hydrochloric acid solution (0.1M, 10 ml) was transferred to a 250 ml beaker, and the solution was diluted to about 100 ml with distilled water. Also, the
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  • Winter '15
  • Amir Alimohammad
  • pH, Acid-Base Potentiometric

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