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02 REDOX EQM Electrode Potential C. Y. Yeung (CHW, 2009)p.01 MetalMetal Ions Eqm between Metal & Metal Ions in a Half Cell: M n+ M Electrode [M(s)] Electrolyte.

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Presentation on theme: "02 REDOX EQM Electrode Potential C. Y. Yeung (CHW, 2009)p.01 MetalMetal Ions Eqm between Metal & Metal Ions in a Half Cell: M n+ M Electrode [M(s)] Electrolyte."— Presentation transcript:

1 02 REDOX EQM Electrode Potential C. Y. Yeung (CHW, 2009)p.01 MetalMetal Ions Eqm between Metal & Metal Ions in a Half Cell: M n+ M Electrode [M(s)] Electrolyte [M n+ (aq)] Metal - Metal Ions System M n+ (aq)+ ne - M(s) Reduction Potential / Electrode Potential (E) (unit: V)

2 p.02 Greater tendency to reduce, larger reduction potential. M n+ (aq)+ ne - M(s) Example:E Mg 2+ | Mg = –2.38 V Mg 2+ (aq) + 2e - Mg(s) -ve reduction potential lower tendency to accept e - (FW) BW Rxn is more favorable Mg(s) tends to release e - (i.e. oxidation). i.e. Mg is a reactive metal. measured under standard conditions (p. 203) (Standard Reduction Potential)

3 cell e.m.f. p.03Example:E Mg 2+ | Mg = –2.38 V E Cu 2+ | Cu = V BW rxn favoured:  Mg is a good R.A. FW rxn favoured:  Cu 2+ is a good O.A. Therefore: Mg(s) Mg 2+ (aq) + 2e - Cu 2+ (aq) + 2e - Cu(s) +2.38V+0.34V +) Cu 2+ (aq) + Mg(s) Cu(s) + Mg 2+ (aq) E cell = +2.72V E Mg 2+ | Mg = –2.38 V E Cu 2+ | Cu = V oxidation takes place [Anode] reduction takes place [Cathode] Cell e.m.f. = E cathode – E anode

4 p.04 Mg(s) | Mg 2+ (aq) Cu 2+ (aq) | Cu(s) Cell Diagram ~ presenting an electrochemical cell … anodecathode salt bridge phase boundary Zn(s) | Zn 2+ (aq) Ag + (aq) | Ag(s) E cell = ? V Check p.207 E Zn 2+ | Zn = –0.76 V E Ag + | Ag = V AnodeCathode E cell = – (-0.76) = +1.56V oxidation reduction electrode of anode electrode of cathode

5 p.05Summary: More –ve reduction potential (E), less likely to be reduced, oxidation is more favourable. i.e. stronger reducing power. More +ve reduction potential (E), more likely to be reduced, reduction is more favourable. i.e. stronger oxidizing power. Electrochemical Series (E.C.S.) could be obtained by arranging the standard electrode potentials.

6 p.06Assignment p.212 Check Point 20.5(a) [due date: 7/5 (Thur)] Next …. Other Common Types of Half Cells, Standard Hydrogen Electrode (S.H.E.), Measurement of Standard Electrode Potentials (p ) Past Paper Q.1-2 [K sp ] [due date: 7/5 (Thur)]


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