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REDOX EQM Half Cells with Inert Electrode

p.01. C. Y. Yeung (CHW, 2009). M. M n+. 03. REDOX EQM Half Cells with Inert Electrode. Inert Electrode :. In the metal-metal ion system, metal is the electrode, and metal ion is the electrolyte.

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REDOX EQM Half Cells with Inert Electrode

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  1. p.01 C. Y. Yeung (CHW, 2009) M Mn+ 03 REDOX EQM Half Cells with Inert Electrode Inert Electrode : In the metal-metal ion system, metal is the electrode, and metal ion is the electrolyte. However, if the system does not involve metal, and “inert electrode” is required. (e.g. platinium / graphite)

  2. p.02 <Example 1> Cell Diagram as cathode: Fe3+(aq) , Fe2+(aq) | Pt(s) Fe3+(aq) + e- Fe2+(aq) as anode: Pt(s) | Fe2+(aq) , Fe3+(aq) <Example 2> = +0.77 V = +1.52 V E E MnO4-,Mn2+| Pt Fe3+,Fe2+| Pt MnO4-(aq) + 8H+ + 5e- Mn2+(aq) + 4H2O(l) Pt - e- + e- Cell Diagram FeSO4(aq) + Fe2(SO4)3(aq) Fe2+ as cathode: [MnO4-(aq) + 8H+(aq)] , [Mn2+(aq) + 4H2O(l)] | Pt(s) Fe3+ as anode: Pt(s) | [Mn2+(aq) + 4H2O(l)] , [MnO4-(aq) + 8H+(aq)] Half Cells using Inert Electrode : (1) Metal Ion – Metal Ion Sytem

  3. p.03 = +1.52 V E MnO4-,Mn2+| Pt anode cathode = +0.77 V E Fe3+,Fe2+| Pt Ecell = +1.52 – (+0.77) = +0.75V Cell Diagram Oxidation C(graphite) | Fe2+(aq) , Fe3+(aq) [MnO4-(aq) + 8H+(aq)] , [Mn2+(aq) + 4H2O(l)] | C(graphite) Reduction Exercise Calculate the cell e.m.f. and write the cell diagram of the electrochemical cell shown below in accordance with the IUPAC convention. (ref.: p. 207) [Ref.: p. 210 Example 20-5C]

  4. p.04 <Example> Cell Diagram as cathode: I2(aq) , 2I-(aq) | Pt(s) as anode: Pt(s) | 2I-(aq) , I2(aq) Exercise I2(aq) + 2e- 2 I-(aq) = +0.54 V E I2, I- | Pt Pt Ecell = +0.77 – (+0.54) = +0.23V - e- + e- I2(aq) + I-(aq) I- Cell Diagram: Pt(s) | 2I-(aq) , I2(aq) Fe3+(aq) , Fe2+(aq) | Pt(s) I2 (2) Non-metal Ion – Non-metal Ion Sytem If iron(III) / iron(II) system acts as the cathode, while iodine / iodide acts as the anode, with using platinium as electrodes. Calculate the cell e.m.f. and write the cell diagram. (ref.: p.207)

  5. p.05 <Example 1> Pt E E = -0.35 V = +0.54 V + e- PbSO4 | Pb AgCl | Ag Ag Cell Diagram - e- electrolyte! AgCl as cathode: Cl-(aq) | AgCl(s) | Ag(s) as anode: Ag(s) | AgCl(s) | Cl-(aq) <Example 2> PbSO4(s) + 2e- Pb(s) + SO42-(aq) AgCl(s) + e- Ag(s) + Cl-(aq) Platinium Black coated with Ag and AgCl Cell Diagram as cathode: SO42-(aq) | PbSO4(s) | Pb(s) HCl(aq) as anode: Pb(s) | PbSO4(s) | SO42-(aq) (3) Metal – Sparingly Soluble Salt Sytem i.e. H2SO4 is used as electrolyte.

  6. p.06 Next …. Standard Hydrogen Electrode (S.H.E.), Measurement of Standard Electrode Potentials (p. 197-212) Assignment p.202 Table 20.1…? p.202 Check Point 20.3 [due date: 11/5 (Mon)] p.20.5(b) [due date: 11/5 (Mon)]

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