Acid-Base Titration Curves Essay Sample free essay sample

Learning Aims to understand the titration curves for the undermentioned solutions †¢ a weak acid: acetic acid. CH3COOH. †¢ †¢ †¢ †¢ †¢ a strong acid: hydrochloric acid. HCl. an acidic commercial cleansing agent. a basic commercial cleansing agent. to utilize the titration curves to cipher the per centum of the active ingredients in the commercial cleansing agents. to find the Ka of a weak acid. Procedure Overview †¢ †¢ †¢ †¢ after standardization of the pH electrode and finding of the flow rate for the automatic titration. a NaOH solution is standardized against HCl. a pH titration curve for acetic acid is obtained and its pKa is determined. an unknown sample of Lysol is analyzed for its HCl content utilizing the standardised NaOH. an unknown sample of Liquid Plumr is analyzed for its NaOH and NaOCl content utilizing HCl of known molar concentration. ACID-BASE TITRATION CURVES Report Sheet Determination of flow rate Equation for transition from clip to volume: Titration of HCl pH at equality point volume of NaOH at equality point concentration of HCl volume of HCl Titration of acetic acid pH at equality point volume of NaOH at equality point volume at half-equivalence point pH at half-equivalence point Titration of Lysol weight of beaker with Lysol weight of empty beaker mass of Lysol pH at equality point volume of NaOH at equality point Titration of Liquid Plumr weight of beaker with Liquid Plumr weight of empty beaker mass of Liquid Plumr pH at first equality point volume of HCl at first equality point pH at 2nd equality point volume of HCl at 2nd equality point ACID-BASE TITRATION CURVES Report Sheet Calculations 1. Titration of HCl ( Standardization of NaOH ) a. Determine the moles of HCl. B. Calculate the molar concentration of NaOH. 2. Titration of acetic acid a. Calculate the Ka for acetic acid. 3. Titration of Lysol a. Calculate the per centum HCl in Lysol. 4. Titration of Liquid Plumr a. Calculate the per centum NaOH in Liquid Plumr. B. Calculate the per centum NaOCl in Liquid Plumr. ACID-BASE TITRATION CURVES Questions/Problems 1. Calculate the pH of a solution in which the concentration of the hydronium ion peers 2. 0 ten 10-4 M. 2. If the pH at the half-equivalence point for a titration of a weak acid with a strong base is 4. 60. determine the value of the Ka for the weak acid. 3. When a 0. 5725 g sample of Lysol was titrated with 0. 100 M NaOH. an end point was obtained at 15. 00 milliliter. Calculate the per centum ( by weight ) of hydrochloric acid in the Lysol sample. 4. When a 3. 529 g sample of Liquid Plumr was titrated with 0. 100 M HCl. two end points were obtained. The first end point occurred at 15. 00 milliliter. the 2nd at 42. 00 milliliter. Calculate the per centums of both NaOH and NaOCl in Liquid Plumr. 5. If you did a â€Å"manual† titration. compare the diagrammatically determined equality point and the index determined end point. If you did a â€Å"timed† titration. the indicator-determined terminal point MAY hold passed excessively rapidly to acquire meaningful informations. but try to do a comparing as best you can. ACID-BASE TITRATION CURVES Suggested Answers to Questions/Problems 1. ( A ) Calculate the pH of a solution in which the concentration of the hydronium ion peers 2. 0 ten 10-4 M. pH = log [ H3O+ ] = pH = 3. 70 ( B ) If the pH at the half-equivalence point for a titration of a weak acid with a strong base is 4. 60. determine the value of the Ka for the weak acid. pKa = pH @ ? equality point Ka = 10! 4. 60 = 2. 5 ten 10! 5 2. When a 0. 5725 g sample of Lysol was titrated with 0. 100 M NaOH. an end point was obtained at 15. 00 milliliter. Calculate the per centum ( by weight ) of hydrochloric acid in the Lysol sample. % HCl = ( 15 milliliter HCl soln ) ( 0. 100 mmol NaOH ) ( 36. 5 g ) ( 1 mol ) ( 100 ) = 9. 56 % ( 0. 5725 g sample ) ( 1. 00 ml soln ) ( 1 mol ) ( 103 mmol ) ( 100 ) 3. When a 3. 529 g sample of Liquid Plumr was titrated with 0. 100 M HCl. two end points were obtained. The first end point occurred at 15. 00 milliliter. the 2nd at 42. 00 milliliter. Calculate the per centums of both NaOH and NaOCl in Liquid Plumr. 1st equality point = HCl responding with NaOH = 15. 00 ml 2nd combining weight. point = HCl responding with NaOCl = 42. 00 milliliter! 15. 00 ml = 27. 00 ml 4. If you did a â€Å"manual† titration. compare the diagrammatically determined equality point and the index determined end point. If you did a â€Å"timed† titration. the indicator-determined terminal point MAY hold passed excessively rapidly to acquire meaningful informations. but try to do a comparing as best you can. The index determined end point is noticeable before the equality point. A swoon pink colour begins to look before the equality point is reached. log ( 2. 0 ten 10-4 ) ACID-BASE TITRATION CURVES Tips and Traps 1. 2. Lysol and Liquid Plumr should be dispensed in a fume goon. utilizing an automatic dispenser. if possible. Students should find the flow rate three times and average the consequence. Flow rate should be determined for each titration individually. ACID-BASE TITRATION CURVES Sample Data Determination of flow rate Equation for transition from clip to volume: Titration of HCl pH at equality point volume of NaOH at equality point concentration of HCl volume of HCl Titration of acetic acid pH at equality point volume of NaOH at equality point volume at half-equivalence point pH at half-equivalence point Titration of Lysol weight of beaker with Lysol weight of empty beaker mass of Lysol pH at equality point volume of NaOH at equality point 67. 5794 65. 6321 1. 9473 7. 0 40. 56 ml g g g 8. 4 21. 50 10. 75 4. 7 ml milliliter 7. 0 20. 6 0. 100 25. 00 ml M milliliter ACID-BASE TITRATION CURVES Sample Data ( page 2 ) Titration of Liquid Plumr weight of beaker with Liquid Plumr weight of empty beaker mass of Liquid Plumr pH at first equality point volume of HCl at first equality point pH at 2nd equality point volume of HCl at 2nd equality point Calculations Titration of HCl ( Standardization of NaOH ) 1. Determine the moles of HCl. 0. 100 M x 0. 02500 L = 0. 00250 mol 2. Calculate the molar concentration of NaOH. at equality point: mol NaOH = mol HCl [ NaOH ] = 0. 00250 mol = 0. 121 M 0. 0206 L Titration of acetic acid 1. Calculate the Ka for acetic acid. pKa = pH1/2 = 4. 7 Ka = 10-4. 7 = 2. 0 ten 10! 5 67. 8074 65. 6321 2. 1753 9. 2 9. 20 4. 7 13. 6 ml milliliter g g g Titration of Lysol 1. Calculate the per centum HCl in Lysol. % HCl = ( 40. 56 ml NaOH ) ( 0. 121 mmol NaOH ) ( 36. 5 g ) ( 1 mol ) ( 100 ) = 9. 23 % ( 1. 9743 g sample ) ( 1. 00 ml soln ) ( 1 mol ) ( 103 mmol ) ( 100 ) ACID-BASE TITRATION CURVES Sample Data ( page 3 ) Titration of Liquid Plumr 1. Calculate the per centum NaOH in Liquid Plumr. % NaOH = ( 9. 20 ml HCl ) ( 0. 100 mmol HCl ) ( 40. 0 g ) ( 1 mol ) ( 100 ) = 1. 69 % ( 2. 1753 g sample ) ( 1. 00 ml soln ) ( 1 mol ) ( 103 mmol ) ( 100 ) Calculate the per centum NaOCl in Liquid Plumr. % NaOCl = ( ( 13. 6-9. 2 ) milliliter HCl ) ( 0. 100 mmol NaOH ) ( 74. 4 g ) ( 1 mol ) ( 100 ) = 1. 51 % ( 2. 1753 g sample ) ( 1. 00 ml soln ) ( 1 mol ) ( 103 mmol ) ( 100 ) Sample Titration Curves HOAc titration curve with first derived function. Combined HCl A ; HOAc idealized titration curves ACID-BASE TITRATION CURVES Laboratory Preparation ( per pupil station ) Equipment †¢ two 250-ml beakers †¢ 150-ml beaker †¢ 50-ml buret †¢ buret clinch †¢ 25-ml graduated cylinder †¢ 10-ml graduated cylinder †¢ glass stirring rod †¢ glass funnel ( short root ) †¢ pH electrodes + stands w/ clinch †¢ timer Supplies †¢ towel Chemicals Exact measures needed are listed below. A minimal 50 % surplus is recommended. †¢ 2. 5 M NaOH. 10 ml †¢ 0. cubic decimeter M HCl. 50 ml †¢ 0. cubic decimeter M CH3COOH. 25 ml †¢ pH 4. 7 and 10 buffer solutions. 15 ml each. reclaimable †¢ Lysol. 2 ml †¢ Liquid Plumr. 2 ml Safety and Disposal †¢ Lysol: grip with attention – strongly acidic. Can be flushed down drain with tonss of H2O †¢ Liquid Plumr: grip with attention – strongly basic.