Titrasi redoks
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Titrasi redoks
- 2. Analisis kuantitatif klasik Acid-base Standardization Chromatography Permanganimetric Gravimetry Redox Titrations Fajans Preciptation Complexometric
- 3. Analisis kuantitatif klasik Titrasi Asam-basa pengendapan kompleksometri Redox Gravimetri
- 4. Analisis kuantitatif klasik Titrasi Asam-basa pengendapan kompleksometri Redox Titrasi melibatkan iodine (I2) Iodimetri Iodometri Gravimetri dikromatometri permanganometri
- 5. Contoh titrasi Analit Titran Indikator Asam-basa Kadar asam asetat dalam minuman Asam asetat (CH3COOH) NaOH (sodium hydroxide) Phenolphthalein kompleksometri Mengukur kesadahan air (kalsium & magnesium) Kalsium dan magnesium (Ca 2+ , Mg 2+ ) EDTA Eriochrome black T Murexide Pengendapan Penentuan kadar klorin dlm air klorin AgNO3 (silver nitrate) Mohr, Volhard, Fajans Redox Penentuan kadar hidrogen peroksida (H2O2) Hidrogen peroksida (H2O2) KMnO4 (potassium permanganate) Tanpa indikator
- 6. Redox Titrations Titrasi Redoks Berdasarkan pada reaksi reduksi-oksidasi antara analit dan titran Banyak senyawa kimia, biologi, lingkungan, dan lainnya dapat ditentukan kadarnay dengan titrasi redoks Biochemistry 2005, 44, 1856-1863 Measurement of redox potentials permit detailed analysis of complex enzyme mechanism Electron path in multi-heme active site of P460
- 7. Redox Titrations terjadi perubahan voltase seiring dengan penambahan titran Contoh reaksi pada titrasi redoks berikut (reaksi berjalan sempurna): Ce4+ ditambahkan dari buret pada larutan Fe2+ Elektroda Pt merespon perubahan konsentrasi dari: Fe3+ /Fe2+ & Ce4+ /Ce3+ Elektroda Kalomel digunakan sebagai referensi Eo = 0.767 V K ≈ 1016 Eo = 1.70 V
- 8. Ada beberapa jenis titrasi redoks yang diklasifikasikan berdasarkan titran yang digunakan. 1) Permanganometri: Titran KMnO4 2) Dikromatometric Titran K2Cr2O7 3) Titrasi melibatkan iodine (I2) •Iodimetri •Iodometri Titrasi yang menggunkaan I2 termasuk jenis titrasi yang sering digunakan.
- 9. Pereduksi adalah senyawa yang dalam reaksi redoks mereduksi senyawa lain, dengan kata lain bertindak sebagai oksidator, dan sebagai donor elektron dalam reaksi redoks. Contoh senyawa pereduksi: Logam natrium, magnesium, aluminium, dan zink NaH, CaH2, dan LiAlH4, senyawa yang mengandung ion H- .
- 10. Oksidator adalah senyawa yang dalam reaksi redoks mengoksidasi senyawa lain, dengan kata lain bertindak sebagai reduktor dan sebagai penangkap elektron. Contoh : permanganat (MnO4 - ), chromat (CrO4 2- ), dan dichromat (Cr2O7 2- ), natrium hipoklorit (bleach), asam nitrat (HNO3), asam perklorat (HClO4), dan asam sulfat (H2SO4)
- 11. Titrasi dengan permanganat Kalium Permanganat (KMnO4) - Oksidator kuat - Auto indikator Titration of VO2+ with KMnO4 Before Near After Equivalence point Eo = 1.507 V Violet colorless pH ≤ 1 Eo = 1.692 V pH neutral or alkaline Violet brown pH strolngly alkaline Eo = 0.56 V Violet green
- 12. Titrasi iodimetri Iodimetri: titrasi langsung dengan satu tahap reaksi : Analit + titran (iodine I2 ) produk (iodide I→ - ) Tdk diketahui diketahui Bila titrasi dilakukan dengan titran iodin maka disebut titrasi iodimetri
- 13. Titrasi iodimetri Contoh : penetapan kadar asam askorbat (Vitamin C) C6H8O6 + I2 → CçH6O6 + 2I- + 2H+ Iodin mengoksidasi dengan cepat asam askorbat C6H8O6 , dan menghaslkan asam dehidroaskorbat, C6H6O6 . Asam askorbat asam dehidroaskorbat Pictures taken from: http://en.wikipedia.org
- 14. Titrasi iodometri Iodometri adalah titrasi terhadap iodin (I2) yang dihasilkan dari oksidasi analit terhadap I- yang ditambahkan. Kemudian iodin (I2) biasanya dititrasi dengan larutan standar tiosulfat. Iodometri: bukan titrasi langsung karena tejadi 2 reaksi: analit + I- → I2 Tdk diketahui I2 + titran (standar tiosulfat) produk→ diketahui
- 15. Titrasi iodometri Contoh : penetapan kadar tembaga Analit dgn konsentrasi tdk diketahui Titran -larutan standar : natrium tiosulfat -konsentrasi diketahui 2 Cu 2+ + 4I- → 2CuI + I2 I2 + 2S2 O3 2- → 2I- + S4 O6 2-
- 16. Titrasi Iodimetri: a) Reduksi analit b) Satu reaksi c) Larutan standar: Iodin (I2) Titrasi Iodometri: a) Oksidasi analit b) Dua reaksi c) Larutan standar: natrium tiosulfat
- 17. Aplikasi analisis: titrasi Iodimetri: senyawa yang dianalisis SO2 H2S Zn2+ , Cd2+ , Hg2+ , Pb2+ Cisteine, glutathione, mercaptoethanol Glucose (dan gula-gula pereduksi lain) Section of a protein structure Source: http://en.wikipedia.org
- 18. Aplikasi analisis: Titrasi Iodometri: Senyawa yang dianalisis HOCl Br2 IO3 - , IO4 - O2, H2O2, O3 NO2 - Cu 2+ MnO4 - , MnO2
- 19. Kedua : Pre-treatment sample Contoh : titrasi Iodometri untuk tembaga Sample: kawat tembaga (solid) Pertama : larutkan sample kawat tembaga Cu0 dissolution→ → Cu 2+ Ion tembaga: oksidator
- 20. Ketiga: titrasi Iodometri Analit dgn konsentrasi tdk diketahui Titran -larutan standar : natrium tiosulfat -konsentrasi diketahui 2 Cu 2+ + 4I- → 2CuI + I2 I2 + 2S2 O3 2- → 2I- + S4 O6 2-
- 21. Good luck
Editor's Notes
- Slide 2: Titrations are one of the two types of Classical Quantitative Analysis. What is the other classical quantitative analysis? Exactly, the other classical quantitative chemical analysis is gravimetry. You will see gravimetry in other parts of the course. Let’s continue by asking about titrations. What are the four types of titrations? Yes, remember the four types are: Firstly, acid-base titrations, secondly complexometric titrations, thirdly precipitation titrations and fourthly redox titrations. Remember that we started working with acid-base titrations, then we moved on to complexometric titrations and finally we saw precipitation titrations. Today we will be looking at iodometric and iodimetric titrations, which are examples of redox titrations. We have left redox titrations until now, because you needed to be familiar with the other three type of titrations. So, let’s look at redox titrations in more detail. Do you remember other redox titrations that we have done in the laboratory? Yes, we have done other redox titrations like the determination of the percent of hydrogen peroxide and other ones. Now, we are going to look at the redox titrations involving iodine. Notice here that there are two types of redox titrations involving iodine. The most important thing in this presentation is for you to understand the differences between iodometric and iodimetric titrations. Both involve iodine, but as you will see there are some differences. The analysis that we will perform in the laboratory is the iodometric titration of cooper, which is a classical quantitative chemical analysis, a redox titration involving iodine. It is used because it is necessary to quantify copper in water, alloys, minerals and so on
- Slide 5: As we saw in slide 2, we classify redox titrations according to the titrant which is being used. There are a lot of redox titrations and the most common ones are: First we have Permanganimetric redox titrations where the titrant is KMnO4 (Potassium permanganate). Then we have dichromatometric redox titrations where the titrant is K2Cr2O7 (Potassium dichromate). And finally the titrations that interest us today are the titrations involving iodine (I2). We divide these titrations into two types. Iodimetry –that is, i-o-DI-metry Iodometry – and i-o-DO-metry Notice that the two names are very similar; the objective of this talk is for you to learn the difference between the two types. As we said before titrations that create or consume I2 are widely used in quantitative analysis.
- Slide 7: Now let’s move on to iodometric titrations Unlike iodimetric titrations , in the iodometric ones two reactions are involved. Let’s analyze these two reactions. In this case the analyte is an oxidizing agent. Consequently, in the first reaction The analyte reacts with an excess of iodur to generate iode
- Slide 8: To summarise the main information about iodimetric and iodometric titrations: In iodimetric titrations: The anlyte is a reducing agent. One reaction is involved. The standard solution is Iodine (I2) On the other hand in iodometric titrations: The analyte is an oxidizing agent. Two reactions are involved. The standard solution is sodium thiosulfate.