1. Lecture 14 Redox Titrations

3. aA nalyte + bT itrant  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)

4. Titrant solutions are stable and their concentrations can be easily established by the simple procedures K 2 Cr 2 O 7 - 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

5. Oxidants: Ce IV MnO 4 - Cr 2 O 7 2- BrO 3 - IO 3 - I 2 strong Weak, selective

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

8. E min =0.77 + 0.06  3= 0.95 0.01 M K 2 Cr 2 O 7 [Cr 3+ ]=10 -2 M [Cr 2 O 7 2- ]=10 -5 M [H + ]=1 M E  1.3V 1.0 1.3 0.8 99.9% 100.1%

10. E min = 0.77+0.03  3=0.86 -E(SCE) E max = 1.24-0.015  3=1.19 -E(SCE) @ 1M HCl

12. BrO 3 - + 5Br - + 6H +  3Br 2 + 3H 2 O

13. Starch

14. I