IB›IB Chemistry HL›Mind mapsR3.2 Electron transfer reactionsIB Chemistry HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsRedox basicsOxidation is loss of electronsOxidising agent is reducedBalance half-equations: H₂O, then H⁺, then e⁻MnOX4X−+8 HX++5 eX−→MnX2++4 HX2O\ce{MnO4- + 8H+ + 5e- -> Mn^2+ + 4H2O}MnOX4X−+8HX++5eX−MnX2++4HX2OCellsAnode = oxidation, cathode = reductionVoltaic: spontaneous, anode is negativeElectrolytic: driven by power, anode is positiveVoltaic electrons flow anode → cathodeSecondary cells are recharged by reversingElectrode potentialsMeasured against the standard hydrogen electrode (0.00 V)More positive E⦵: stronger oxidising agentEcell⊖=Ecathode⊖−Eanode⊖E^{\ominus}_{cell} = E^{\ominus}_{cathode} - E^{\ominus}_{anode}Ecell⊖=Ecathode⊖−Eanode⊖Positive E⦵cell: spontaneousNever multiply E⦵ by coefficientsRedoxelectron transferE⊖E^{\ominus}E⊖FFFe⁻Gibbs linkΔG⊖=−nFEcell⊖\Delta G^{\ominus} = -nFE^{\ominus}_{cell}ΔG⊖=−nFEcell⊖F = 96 500 C mol⁻¹Positive E⦵cell gives negative ΔG⦵Answer is in J: divide by 1000ElectrolysisCathode: more positive E⦵ is reducedNa⁺, K⁺, Mg²⁺ stay: water gives H₂Anode is usually water, giving O₂Concentrated NaCl gives Cl₂Copper anode dissolves; graphite gives O₂PlatingObject is the cathodePlating metal is usually the anodeElectrolyte concentration stays constantSilver cathode: AgX++eX−→Ag\ce{Ag+ + e- -> Ag}AgX++eX−Ag