SOR, energy change, redox

dohnotes Speedofreaction=howfastorhowslowareactionis-doanexperimenttomeasurechangeoveraperiodoftime(equations):-amtofreactantusedup/timetaken-amtofproductobtained/timetaken-volofgasproduced/timetaken Experimentnotes:H2isgivenoff:usegassyringe-H2isverylightandthechangeisminimalleadingtounreliableresultsCO2givenoff:masschange-CO2isaheaviergasCottonwool:allowgastoescapeandpreventsolutionfromsplashingGraphsofmass-doesnotreachzero Collisiontheory:-forareactiontotakeplace,theremustbeacollisionbetweenreactantparticles,someareunsuccessful.-asuccessfulcollisionisonewherethecollidingparticleshaveenoughenergytoreact(minimumactivationenergy) Catalyst(usuallytransitionmetals/oxides):=asubstancethatspeedsupachemicalreaction,withoutbeingusedupitself-changethespeedofreaction,nottheyieldofproductobtained-smallamounts→significanteffectsIndustryuse:reducefuelbillsifthereactionisfastenoughatlowertemperaturenote:catalystslowertheactivationenergyofareaction Factors:1.Particlesize-thesmallerthesize,thefasterthereaction-smallerparticlesize=largertotalsurfaceareaforcollisionoftheparticles=higherfrequencyofcollision=higherfrequencyofeffectivecollisionapplication:coaldustburnsfasterthanlargepiecesofcoal=powderedcoalisusedinmoderncoal-burningpowerstations-explosionscanoccuriftheaircontainstoomuchcoaldust(sparksfrommachinerycausesexplosion)=removedustbysprayingwater 2.Concentration-thehighertheconcentration,thefasterthereaction-higherconcentration=greaternumberofreactantparticlesinaunitvolume=higherfrequencyofcollision=higherfrequencyofeffectivecollision 3.Pressure-thehigherthepressure,thefasterthespeedofreaction-higherpressure=particlesareclosertogether=higherfrequencyofcollision=higherfrequencyofeffectivecollision 4.Temperature-thehigherthetemperature,thefasterthereaction-highertemperature=particlespossessmoreke=moveathigherspeedsandcollidewitheachotherwithgreaterforce=greaternumberofparticleswiththeminimumactivationenergy=higherfrequencyofcollision=higherfrequencyofeffectivecollision

dohnotes Heatofreaction(energychange)Enthalpychange:theamountofenergyabsorbedorreleasedinachemicalreactioncarriedoutunderconstantpressure Δ H=HEATABSORBEDDURINGBONDBREAKING-HEATRELEASEDDURINGBONDFORMING Exothermicreactions-givesoutheattothesurroundings(feelshot)Characteristics:-tempofsurroundingsincrease-productshavelessenergythanreactants-negativeΔ H(tempincreasesrapidlyafterthereactionbeginsasheatenergyisgivenofftotheenvironment,tempfallsgraduallyafterreactioniscompleteandreturnstoroomtemp)*thetotalamountofenergyabsorbedinbreakingthebondsinthereactantsisLESSTHANthetotalamountofenergyreleasedfrombondformingintheproducts Endothermicreactions-takesinheatfromsurroundings(feelscold)Characteristics:-tempofsurroundingsdecrease-productshavehigherenergythanreactants-positiveΔ H(tempdecreasesrapidlyafterthereactionbeginsasheatenergyistakeninfromtheenvironment,tempgraduallyincreasesafterreactioniscompleteandreturnstoroomtemp)*thetotalamountofenergyabsorbedinbreakingthebondsinthereactantsisMORETHANthe