IB›IB Chemistry SL›Mind mapsR3.2 Electron transfer reactionsIB Chemistry SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsOxidation statesOxidation = loss of electronsReduction = gain of electronsElements are 0; sum equals the chargeO is −2 (−1 in peroxides), F always −1Oxidising agent is reducedCrX2OX7X2−\ce{Cr2O7^2-}CrX2OX7X2−: 2x − 14 = −2, so Cr is +6Half-equationsBalance atom, then H₂O, then H⁺, then e⁻MnOX4X−+8 HX++5 eX−→MnX2++4 HX2O\ce{MnO4- + 8H+ + 5e- -> Mn^2+ + 4H2O}MnOX4X−+8HX++5eX−MnX2++4HX2OMultiply so the electrons cancelReactivityDown groups 1 and 2: easier to oxidiseDown group 17: oxidising strength fallsClX2+2 BrX−→2 ClX−+BrX2\ce{Cl2 + 2Br- -> 2Cl- + Br2}ClX2+2BrX−2ClX−+BrX2More reactive metal displaces less reactiveMetals above hydrogen react with dilute acidsRedoxelectron transfere⁻OILRIGVoltaic cellsOxidation at anode, reduction at cathodeVoltaic: anode is negativeElectrons flow anode to cathode through the wireSalt bridge: anions to anode, cations to cathodeRecharging reverses discharge half-equationsElectrolysisDrives a non-spontaneous reactionAnode is positive, cathode negativeSolid ionic compounds do not conduct: ions fixedMolten PbBrX2\ce{PbBr2}PbBrX2 cathode: PbX2++2 eX−→Pb\ce{Pb^2+ + 2e- -> Pb}PbX2++2eX−PbOrganic redoxAcidified dichromate: orange → green1° alcohol → aldehyde → carboxylic acid2° alcohol → ketone; 3° not oxidisedLiAlHX4\ce{LiAlH4}LiAlHX4 reduces acids; NaBHX4\ce{NaBH4}NaBHX4 reduces ketones