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1、Generation of electrode potential:The tendency of dissolution of relatively active metals is greater than that of deposits.The tendency of deposition of relatively inactive metals is greater than that of dissolution.DissolutionM(s)Mn+(aq)+ne Deposition 2.Electromotive force of Galvanic cellThe EMF o
2、f the primary cell is equal to the positive electrode potential E(+)minus the negative electrode potential E(-).EMF can be measured by potential difference meter.E EMF=E=E(+)-E-E(-)EMF-electromotive forceEMF -standard electromotive forceQuestion:what is the electrode potential of redox pair?E EMF =E
3、=E(+)-E-E(-)EMF =E(Cu2+/Cu)-E (Zn2+/Zn)Standard hydrogen electrodeThe electrode was coated with black platinum wire and inserted into H+(1 moldm-3)solution,and H2(1.013 10+5 Pa)was introduced into the solution2H+(aq,1mol L-1)+2e=H2(g,100 kPa)(Pt)|H2(100kPa)|H+(1mol L-1)E(H+/H2)=0.000 V 0.34 V 0 V 0.
4、34 V For example:the galvanic cell is composed of standard hydrogen electrode and standard copper electrode.From the formula E E E Get E E E()Pt|H2(p )|H(1 moldm-3)Cu 2(1 moldm-3 )|Cu()The electromotive force of the battery was measured E 0.34 VE Calomel electrode(SCE)Standard hydrogen electrode is
5、very important in practical measurement.As compared with standard hydrogen electrode,the main reason is that hydrogen is not easy to be purified,the standard pressure is not easy to control,and platinum black is easy to be poisoned.Electrode reaction:Hg2Cl2 +2e =2Hg +2Cl-Electrode symbol:Pt,Hg|Hg2Cl2|KCl(saturated)Or KCl(saturated)|Hg2Cl2|Hg,Pt)L2.8mol(Cl (s)ClHg (l)Hg，Pt122Representation method:-KCl(L2.8mol)Cl(1Saturated solution)Saturated calomel electrode:-=c1-=Lmol0.1)Cl(Standard calomel electrode:cE(Hg2Cl2/Hg)=0.2415V-+)aq(Cl 22Hg(l)2e(s)ClHg The electrode reaction:22V268.0/Hg)Cl(Hg22=E