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CHEM 302 (14)
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Chapter 11 Problems.pdf

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Department
Chemistry
Course
CHEM 302
Professor
Michael Wheeler
Semester
Fall

Description
220PROBLEMS11 1Sources of COThetwoprincipalsourcesofCOtotheatmosphereareoxidationofCHand4combustionMeanrateconstantsforoxidationofCHandCObyOHinthe431531113tropospherearek25x10cmmoleculesandk15x10cm1211moleculesrespectivelyObservationsindicatemeanCOconcentrationsof80ppbvinthenorthernhemisphereand50ppbvinthesouthernhemisphereandagloballyuniformCHconcentrationof1700ppbvCalculatethefractionofthe4COsourceineachhemispherecontributedbyoxidationofCHCommenton4the interhemispheric difference11 2Sources of tropospheric ozone1OzoneissuppliedtothetropospherebytransportfromthestratosphereWeestimateherethemagnitudeofthissourcebyusingthetwoboxmodelforstratospheretroposphereexchangeintroducedinproblem33wherek07ST1yristhetransferrateconstantofairfromthestratospheretothetroposphere1014yristhereversetransferrateconstantfromthetropospheretoandkTS13thestratosphereObservationsindicatethattheatmospherecontains5x10molesofOandthat90ofthattotalisinthestratospheretheremaining10is3inthetroposphereCalculatethenetsourceoftroposphericOcontributedby3transport from the stratosphere2OzoneisalsoproducedwithinthetropospherebyoxidationofCOandhydrocarbonsprincipallyCHinthepresenceofNOOneoftheearliest4xestimatesoftheglobalsourceofozoneinthetropospherewasdonebyscalingtheemissioninventoriesofCHandCOWerepeatthiscalculationhere4ConsiderthefollowingmechanismforoxidationofCHandCOtoCOunder42highNO conditionsxO2CHOHCHOHO4322CHONOCHONO3232CHOOCHOHO3222O2NOhnNOO23HONOOHNO22OOHCHOHOCH22221CHOOCOHO22O2COOHCOHO2221WriteanetreactionfortheoxidationofCOtoCObytheabovemechanism2toCOsomeofthereactionsmayproceedDothesamefortheoxidationofCH42morethanonceHowmanyOmoleculesareproducedpermoleculeofCO3oxidized per molecule of CH oxidized413122Presentdayglobalemissionestimatesare3x10molesyrforCHand41314x10molesyrforCOUsingyourresultsfromquestion21estimatetheglobal production rate of ozone in the troposphere23Therangeofestimatesfortheglobalchemicalproductionrateofozoneinthetroposphereasderivedfrom3dimensionalmodelsoftroposphericchemistryis131molesyrExplainhowtheapproachyouusedinquestion22might610x10be expected to overestimate the production rate of ozone24Concludeastotherelativeimportanceoftransportfromthestratosphereandproduction within the troposphere as sources of tropospheric ozone11 3Oxidizing power of the atmosphere1Consider the mechanism for oxidation of CH to CO42O21CHOHCHOHO4322CHOHOCHOOHO2a32232O2b2CHONOCHONO3222O3a2CHOOHhnCHOHOOH322OOHOHCHOO HHOCH3b322CHOOHOHCHOHO3c3322O4a2CHOhnCO2HO22CHOhnCOH4b22
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