§76 Reversible cell 7. 6. 4 Reversible electrodes Important metal-insoluble salt-anion (2) The second-type electrode electrode metal-insoluble salt-anion electrode Hg( IHg, CL(s)ICr(c) A metal plate coated with insoluble salt containing the metal, and immersed in a Hg, Cl(s)+ 2e>2Hg ()+ 2Cl(c) solution containing the anions of the salt metal insoluble salt anion electrode There are three phases contacting with each other in the electrode AgCl Pb(s)pBsO (S)ISo. 2-(c): in lead-acid battery CI Ag(s) agCl(s) cl- Cl- Cl- PbSO4(S)+2e>Pb(s)+SO4(c) cr Cr AgCI(S)+e=Ag(s)+CI(2) The second-type electrode: metal – insoluble salt-anion electrode A metal plate coated with insoluble salt containing the metal, and immersed in a solution containing the anions of the salt. metalinsoluble saltanion electrode Ag(s)AgCl(s)Cl− Important metal – insoluble salt-anion electrode Hg(l)Hg2Cl2 (s)Cl− (c): Pb(s)PbSO4 (s)SO4 2− (c): in lead-acid battery Hg2Cl2 (s) + 2e− → 2Hg(l) + 2Cl− (c) PbSO4 (s) + 2e− → Pb(s) + SO4 2− (c) There are three phases contacting with each other in the electrode. 7.6.4 Reversible electrodes §7.6 Reversible cell