Lecture 12. pH Titration Curves

Lecture 12. pH Titration Curves - Chapter 10: Chapter...

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Unformatted text preview: Chapter 10: Chapter Acid-Base Titrations Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Titration of a Strong Acid with a Strong Base Titration Before base is added: Treat as a strong acid Before the equivalence point: … At the equivalence point: … After the equivalence point: … Example: Titration of Example: 50.00 mL of 0.050 M hydrochloric acid with 0.10 M NaOH. 14 12 10 8 6 4 2 0 0 pH titrant/ mL 5 10 15 20 25 30 Mixing Strong Acids and Weak Bases Mixing A strong acid, HX, completely reacts with a weak base, A. Before the equivalence point: c X = c HA Example: Example: Solution A, prepared from Solution • 10 mL 1.0 M HCl 10 • 20 mL 1.0 M sodium acetate 20 • Filled to 100 mL in volumetric flask. Filled Solution B, prepared from • 10 mL 1.0 M acetic acid 10 • 10 mL 1.0 M sodium acetate 10 • 10 mL 1.0 M sodium chloride 10 • Filled to 100 mL in volumetric flask. Filled Both solutions: cCl = cHA = cA = 0.1 M Cl Mixing Strong Bases and Weak Acids Mixing A strong base, MOH, completely reacts with a weak acid, HA. Before the equivalence point: cM = cA Example: Example: Solution A, prepared from Solution • 10 mL 1.0 M NaOH 10 • 20 mL 1.0 M acetic acid 20 • Filled to 100 mL in volumetric flask. Filled Solution B, prepared from • 10 mL 1.0 M acetic acid 10 • 10 mL 1.0 M sodium acetate 10 • Filled to 100 mL in volumetric flask. Filled Both solutions: cNa = cHA = cA = 0.1 M Na The Exact H+ Equivalent of the “HendersonExact Hasselbalch” Equation c HATotal - [H + ] + K w [H + ] + [H ] = K a ´ c Atotal + [H + ] - K w [H + ] The Exact H+ Equivalent of the “HendersonExact Hasselbalch” Equation c HATotal - [H + ] + K w [H + ] + [H ] = K a ´ c Atotal + [H + ] - K w [H + ] pH cStrongBase/ M Titration of a Weak Acid with a Strong Base Titration Before base is added: Treat as a weak acid weak Before the equivalence point: Treat as a buffer as At the equivalence point: Treat as a weak base weak After the equivalence point: pH is determined by excess OHdetermined Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Titration of a Weak Acid with a Strong Base Titration Example: Calculate the pH at 0, Example: 25, 50 and 60 mL titrant in a titration of 50.00 mL of 0.100 M acetic acid with 0.100 M NaOH. (Ka acetic = 1.75 x 10-5) 1.75 Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Titration of a Weak Acid with a Strong Base Titration Gary D. Christian, Analytical Chemistry, 6th ed., John Wiley & Sons, Inc., U.S.A., 2004. Titration of a Strong Base with a Strong Acid Titration H+ + O HH2O Before the equivalent point: pH is determined by excess OHdetermined At the equivalence point: pH is determined by autoprotolysis of H2O determined After the equivalence point: pH is determined by excess H+ determined Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman Titration of a Strong Base with a Strong Acid Titration H+ + O HH2O Example: Calculate the pH after 50.00 mL of 0.100 M NaOH has been titrated with 0.00, 5.00, 50.00 and 55.00 mL of 0.100 M HCl. and Daniel C. Harris, Exploring Chemical Analysis, 2nd ed., W.H. Freeman and Company, New York, 2001. Freeman ...
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This note was uploaded on 04/06/2011 for the course CHEM 2011 taught by Professor Buhlman during the Spring '10 term at Minnesota.

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