ZNOTES.ORGUPDATED TO 2022 SYLLABUSCAIE A2 LEVELCHEMISTRY (9701)SUMMARIZED NOTES ON THE THEORY SYLLABUSCAIE A2 LEVEL CHEMISTRY (9701)1.5.Born-Haber Cycle1.Chemical Energetics.A of an element under standard conditions=01.1.Enthalpy change of AtomizationEndothermic Processes:Bottom to top:·Enthalpy change of atomization(△FHat上enthalpy changewhen 1 mole of gaseous atoms is formed from its△elements under standard conditions·eg:Na(s)→Na(g△H·eg:1/2d2(g→d(gNote:specific value may not be given and you must usecombination of enthalpies e.g.Exothermic Processes:Top to bottom:Br2(l)Br(g)1.2.Lattice Energy(nen-metal)Lattice Energy (AH):enthalpy change when one moleof an ionic compound is formed from its gaseous ions(non-metal)under standard conditions.gaseous element+element·More-ve△Hat→stronger ionic bonding→more(non-metsl)Hestable ionic compoundIf theoretical and experimental value similar,bonding is pure ionic,otherwise it is intermediatebetween ionic and covalentCompound1.3.Factors Affecting Lattice Energy1.6.Dissolving SaltsCharge on IonEnthalpy change of solution(H):enthalpy changeRadius of Ionwhen one mole of ionic solid is dissolved in sufficientRadius of ion:the smaller the radius/smaller the size ofwater to form a very dilute solution under standardion,greater the charge densityconditions (can be +ve or -ve)Charge on ion:Greater charge density,greaterelectrostatic attraction between ions,A moreEnthalpy change of hydration(H):enthalpy changeexothermic,more stable compoundwhen one mole of specified gaseous ions dissolves insufficient water to form a very dilute solution under1.4.Electron Affinitystandard conditionse.g.Na"(g)+aq→Na(aq)·First electron Affinity(△FHga上enthalpy change when1·Factors affecting△Hhyd=factors affecting△H°atmole of electrons is added to 1 mole of gaseous atoms toSolubility of ionic salts depend on value of theform 1 mole of gaseous anions under standardmore -ve more solubleconditions1.7.lon Polarization1st electron affinity is exothermic2nd,3rd...electron affinities are endothermic becauselon polarization:distortion of the electron cloud on anwhen electron added to -ve ion,increased repulsionanion by a neighbouring cationpresent therefore requires input of energyWWW.ZNOTES.ORGCAIE A2 LEVEL CHEMISTRY (9701)Polarizing power:ability of a cation to attract electronsand distort and anionPolarization will be increased by:Cation has a higher charge density:high positiveanodecathodecharge and small size(positive)(negative)Anion has greater polarizability:high negative chargeand large sizeoxidationelectron loss1.8.Thermal Stability of Gp.2 CO3 andanionselectron gain(negative)cationspositive)Down the group,polarizing power decreaseselectrolyte·Mg2+>Ca2+>Sr2+>Ba2+The greater the polarization,the more distorted is theElectrolyte:compound that is decomposed (molten/ionic)anion causing it to weaken the C-O bondElectrodes:rods which allow current to enter electrolyteTherefore,easier to form CO2 and XO and compound less(inert/reactive)stable..Order of stability:Ba2+>Sr2+>Ca2+>Mg2+2.2.Product of Electrolysis1.9.Solubility of Gp.2 HydroxidesMolten Electrolyte:SulphatesAt the cathode:positive ions reduced to atomsRadius of cation increases down group.'.charge densityPb20+2e→Pbs)decreasesAttraction of cation to water molecule decreases.'.valueAt the anode:negative ions oxidized to atoms/molecules.AHlat also decreases but decrease is relatively smallerbecause of large size of anions compared to cations.AF sol becomes less exothermic because decrease inAqueous Electrolyte:At the cathodeAt the anode..solubility of Hydroxide increase and Sulphate decrease>0then metal less>0.4 then non-metaldown the groupreactive than H so metalless reactive than OH soformednon-metal formed2.ElectrochemistryE<0 then metal more<0.4 then non-metalreactive than Hso H2()more reactive than OH soformedH2O()formed2.1.ElectrolysisFollowing results fromyabove,if solution veryElectrolysis:decomposition of a compound into itsConc.dilute,this occurselement by an electric currentgreater:Electrolysis cell:H*2(g)2eZ-2.3.Quantitative ElectrolysisCalculating quantity of charge passed during electrolysis:Q=Itin Coulombs (C)Mass of a substance liberated is proportional to thequantity of electricity which passes through electrolyteWWW.ZNOTES.ORG