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Lecture 14

Lecture 14. Redox Titrations. a A nalyte + b T itrant  c C + d D. products. Requirements:. One reaction with integer coefficients a and b The reaction is fast enough to perform the whole procedure in 20-40 min

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Lecture 14

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  1. Lecture 14 Redox Titrations

  2. aAnalyte+ bTitrant cC+ dD products Requirements: • One reaction with integer coefficients a and b • The reaction is fast enough to perform the whole procedure in 20-40 min • Titrant solutions are stable and their concentrations can be easily established • by the simple procedures • There is an easy way to establish the end point of titration (that is, the • convenient indicator is available)

  3. Titrant solutions are stable and their concentrations can be easily established by the simple procedures K2Cr2O7 - no change in 30 years Primary standard -chemical compound that you can weigh and disolve to prepare solution of known concentration without standartization Requirements: • Purity of at least 99.9% • Stable and easy to purify if necessary • Convenient to weigh • Well soluble and stable in solution • non-toxic, non-expensive Secondary standard -solution of known concentration which was established by titration of the primary standard

  4. Oxidants: CeIV MnO4- Cr2O72- BrO3- IO3- I2 strong Weak, selective

  5. Emax =1.5-0.060.06=1.32 -E(SCE) 100.1% Any potential in this range is be satisfactory Emin =0.77 + 0.063= 0.95 -E(SCE) 99.9%

  6. 1.3 0.01 M K2Cr2O7 E1.3V [Cr3+]=10-2 M [Cr2O72-]=10-5M [H+]=1 M 100.1% 1.0 Emin =0.77 + 0.063= 0.95 0.8 99.9%

  7. Emax = 1.24-0.0153=1.19 -E(SCE) @ 1M HCl Emin = 0.77+0.033=0.86 -E(SCE)

  8. BrO3- + 5Br- + 6H+ 3Br2 + 3H2O

  9. Starch

  10. I

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