IGCSE›Cambridge IGCSE Chemistry›Mind mapsElectrolysisCambridge IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsHow it worksBreaks down a molten or aqueous ionic compoundIons must be free to move, so solids failAnode is positive: oxidationCathode is negative: reductionAnions go to the anode, cations to the cathodeMolten compoundsMetal forms at the cathodeNon-metal forms at the anodePbX2++2 eX−→Pb\ce{Pb^2+ + 2e- -> Pb}PbX2++2eX−Pb at the cathode (molten PbBrX2\ce{PbBr2}PbBrX2)2 BrX−→BrX2+2 eX−\ce{2Br- -> Br2 + 2e-}2BrX−BrX2+2eX− at the anodeBromine is a reddish-brown gasAqueous solutionsHydrogen forms at the cathodeConcentrated halide gives halogen at the anodeDilute solution gives oxygen at the anodeIodide always gives iodine, never oxygenBrine: 2 ClX−→ClX2+2 eX−\ce{2Cl- -> Cl2 + 2e-}2ClX−ClX2+2eX−Electrolysissplitting ionic compoundsanodecathodeCopper electrodesInert electrodes: oxygen at the anodeCopper anode dissolves and loses massCopper cathode gains massSolution stays blue: CuX2+\ce{Cu^2+}CuX2+ is replacedBasis of copper electrorefiningElectroplatingObject to plate is the cathodePlating metal is the anodeElectrolyte contains ions of the plating metalImproves appearance and corrosion resistanceExam tipsWrite half-equations separately for each electrodeBalance atoms and chargeElectrons on the left for reductionChlorine only forms if the solution is concentrated