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Reduction-Oxidation Reactions (1)

Reduction-Oxidation Reactions (1). 213 PHC 11 th lecture (1) Gary D. Christian, Analytical Chemistry,6 th edition. . Titration Curves. By the end of the lecture the student should be able to:. Calculate the potential ( E ) change throughout the titration.

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Reduction-Oxidation Reactions (1)

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  1. Reduction-Oxidation Reactions (1) 213 PHC 11 thlecture (1) Gary D. Christian, Analytical Chemistry,6th edition.

  2. Titration Curves

  3. By the end of the lecture the student should be able to: • Calculate the potential (E) change throughout the titration. • Choose a suitable indicator for redox titration.

  4. Titration curve: Example: Titration of 100 ml 0.1 M Fe2+ versus 0.1 M Ce4+ Fe2+ + Ce4+ Fe3+ + Ce3+ Fe2+ Fe3++ e Ce4+ + e  Ce3+ Oxidation Reduction

  5. Titration Curves Stages: • At beginning of titration: Only Fe2+, E = zero • During titration: E from Nernst eq. of analyte (Fe2+) • At midpoint of titration: E = Eo • At the equivalence point: E = n1Eo1 + n2Eo2 / n1 + n2 • Beyond the e.p. E from Nernst eq. of titrant (Ce4+)

  6. Questions?

  7. Detection Of The End Point

  8. Self-Indication • Highly colored • e.g. potassium permanganate (purple) MnO4- + 5e = Mn2+ (purple) (colorless)

  9. Starch Indicator • Used with iodine • Strach-I2 complex (dark blue)

  10. Redox Indicators • Highly colored dyes • Weak reducing or oxidizing agents • The color of the reduced and oxidized forms are different • Ein =Eoin – 0.059/n log [Red]/[Ox] • The ratio and color will change with E change during titration • Eo of indicator must be near the E of eq. p. • The redoxind. reaction must be rapid • E.g. Diphenylamine

  11. Questions?

  12. Summary: • Potential (E) change calculation during redox titration. • Detection of the end point in redox titration.

  13. Thanks

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