ap chemistry day 16 - ms. flemingflemingapchem.weebly.com/.../ap_chem_week_7_ch_5_a_.pdf · 2020....

Friday,October13th,2017

APChemistryDay16

Do-Now:GroupDiscussion

1.   Solve:Siliconnitride(Si3N4)ismadebycombiningsiliconandnitrogengasatahightemperature.Howmuchsiliconisneededtoreactwithanexcessofnitrogengastoprepare125gramsofsiliconnitrideifthepercentyieldofthereacDonis95.0%?

2.   ReviewwithyourgroupàwewilltakeourCh.3QuizsoonJ

2

CW/HWAssignments

6.  Ch.5NotesPartA10/13

7.  Ch.5Packet10/13

PLANNER •  LabCorrecLonsdueMonday(notTuesday)

•  StudyCh.3&5forquizandunittest•  BringFastTracktoa5books(oraclearpictureofthebarcode)onTuesday

EssenLalknowledgestandards•  2.A.2:ThegaseousstatecanbeeffecLvelymodeledwitha

mathemaLcalequaLonrelaLngvariousmacroscopicproperLes.A

gashasneitheradefinitevolumenoradefiniteshape;becausethe

effectsofa]racLveforcesareminimal,weusuallyassumethatthe

parLclesmoveindependently.

•  2.B.3.:Intermolecularforcesplayakeyroleindeterminingthe

properLesofsubstances,includingbiologicalstructuresand

interacLons.

•  3.A.2:QuanLtaLveinformaLoncanbederivedfromstoichiometric

calculaLonsthatuLlizethemoleraLosfromthebalancedchemical

equaLons.Theroleofstoichiometryinreal-worldapplicaLonsis

importanttonote,sothatitdoesnotseemtobesimplyanexercise

doneonlybychemists.

•  5.A.1:TemperatureisameasureoftheaveragekineLcenergyof

atomsandmolecules

FLT•  Iwillbeableto:–  UseKMTandconceptsofIMFstomakepredicLonsaboutthe

macroscopicproperLesofgases,includingbothidealand

nonidealbehaviors

–  RefinemulLplerepresentaLonsofasampleofma]erinthegas

phasetoaccuratelyrepresenttheeffectofchangesin

macroscopicproperLesonthesample

–  ApplymathemaLcalrelaLonshipsoresLmaLontodetermine

macroscopicvariablesforidealgases

–  QualitaLvelyanalyzedataregardingrealgasestoidenLfydeviaLonsfromidealbehaviorandrelatethesetomolecular

interacLons

–  RelatequanLLes(includingvolumesandpressuresofgases)to

idenLfystoichiometricrelaLonshipsforareacLon

•  Bycomple1ngCh.5Notes

Ch.5:Gases

KineLcEnergy

Kinetic Energy •  KineLcenergy:EnergyanobjecthasbecauseofitsmoLon

•  Thinkaboutit:Toaccelerateanobject,wemust

applyaforce.Butonceapplied,energyhasbeen

transferredtothemovingobject.

•  KineLcenergyissimplytheenergyanobjecthas

becauseofitsmoLon

KMT •  Allma]erconsistsofLnyparLclesthatarein

constantmoLon.

KMT •  ManyscienLstshavestudiedgasesandaidedwith

thedevelopmentofkineLctheory.Howcouldthey

describetheproperLesofsubstanceswithnofixed

shapeorvolume?

KMT •  ThekineLcmoleculartheorydescribeshow

individualgasparLclesinteractwitheachother

KMT Assumptions 1.   Gasesaremadeofmanyspherical

parDclesthatareinconstant,random

moDon

–  theyhavekineDcenergy

2.   GasparDclesexertneitheraPracDvenorrepulsiveforcesononeanother

3.   GasparDcleshaveinsignificantvolume.

–  ThereissomuchspacebetweenparDclesthatmostofthevolumeisemptyspace

4.   CollisionsareperfectlyelasDc.–  Whentheycollide,nokineDcenergyislost.

5.   AverageKEisdependentonthetemperature.

–  Highertemperatures=Greaterenergy

ProperLesofGases

ProperLesofGases•  Gaseshaveanindefiniteshapeandvolume

•  BecausetheyareinconstantmoLon,gasesexpandtofill

anycontaineruniformly

ProperLesofGases

•  Gasesareeasilycompressed

ProperLesofGases•  Gasesexertpressureontheirsurroundings

Pressure

Gas Pressure •  Pressureisdefinedasforceperunitarea•  Forexample,ahighheelshoeexertsagreater

pressurethananormalshoeduetothesmaller

areaofcontact

•  Largershoesspreadouttheforceoveragreaterarea

Gas Pressure

Gas Pressure •  GasparLclesexertpressurewhentheycollidewiththewallsoftheircontainer

•  Individualgasmoleculesexertaminimalpressure

•  Gaspressureiscausedbycollisionsofmany

parLclesagainstobjects

Air Pressure •  Airisamixtureofgases

Air Pressure •  BecauseairparLclesareinconstantmoLon,theyexert

pressure.

•  Wecallthispressure

“atmosphericpressure”or

“airpressure”

Gas Pressure

Barometer •  Barometer–measuresatmosphericpressure

UnitsofPressure

Converting Between Units of Pressure •  UnitsofPressure:

– Pascal(Pa)–SIunit– Kilopascal(kPa)– Millimetersofmercury(mmHg)

– Atmospheres(atm)

– Torr– psi

Converting Between Units of Pressure •  ConversionFactorsforPressure:•  1atm=760mmHg=760torr=101,325Pa

=101.325kPa

Ex:

•  Pressureofagasismeasuredas49torr

– Representthispressureinbothatmospheresand

pascals

FactorsAffecLngGasPressure

Factors Affecting Gas Pressure FourVariablesforDescribingGases:

1. Pressure(P)(Pa,kPa,atm,etc)

2. Volume(V)(L,mL,etc)3. Temperature(T)inK4. NumberofMoles(n)inmol

•  V,T,andnaffectthePressureofagas

Factors Affecting Gas Pressure Amount(n):

• More molecules means more collisions, and…

•  Fewer molecules means fewer collisions.

• P increases directly with n (ex/ if you double the amount of molecules, you will double the pressure)

Factors Affecting Gas Pressure Volume(V):

•  In a smaller container, the molecules have less room to move.

• The particles hit the sides of the container more often.

• P and V are INVERSELY related – As volume decreases, pressure

increases.

Factors Affecting Gas Pressure Temperature(T):

• Astemperatureincreases,molecules

movefaster

• Astemperaturedecreases,molecules

moveslower

• PandTaredirectlyrelated– Increasingtemperatureincreases

pressure

Pair-Share-Respond

1.   DescribetheparDclesandmoDonofagas

2.   IdenDfythemainideasoftheKineDcMolecularTheory

3.   Whatcausesgaspressure?

4.   IdenDfythreefactorsthataffectgaspressure

5.   StateifthethreefactorsareDIRECTLYorINVERSELYrelatedtopressure

GasLaws

TheGasLaws

• Thegaslawstellushowgasesbehave

• TheamountofchangecanbecalculatedwithmathemaLcal

equaLons.

Boyle’sLaw

RobertBoyle

(1627-1691)

• Boylebecameinterested

inmedicineandthenew

scienceofGalileoand

studiedchemistry.

• AfounderandaninfluenLalfellowofthe

RoyalSocietyofLondon

• Wroteextensivelyon

science,philosophy,and

theology.

Boyle’sLaw

• WhenTisheldconstant,Pisinversely

proporLonaltoV

Boyle’sLaw

•  EquaLons:•  PV=k•  P1V1=P2V2

•  (Tmustbe

constant)

Boyle’sLaw

• WhatwouldthegraphlooklikeifitwasP

against1/V?

Boyle’s Law Ex/ •  Sulfurdioxide,agasthatplaysacentralroleintheformaLonofacidrain,isfoundintheexhaustof

automobilesandpowerplants.

•  Considera1.53-Lsampleofgaseoussulfurdioxideata

pressureof5.6x103Pa.Ifthepressureischangedto

1.5x104Paataconstanttemperature,whatwillbe

thenewvolumeofthegas?

Boyle’s Law Ex/ •  Considera1.53-Lsampleofgaseoussulfurdioxideata




•  SoluLon•  First,writewhatyouknow:•  P

1=

•  V1=

•  P1=

•  P2=





•  SoluLon•  Second,writeyourequaLon:P

1V1=P

2V2

•  P1=

•  V1=

•  P1=

•  P2=





•  SoluLon•  Third,isolateandsolveP

1V1=P

2V2

•  P1=

•  V1=

•  P1=

•  P2=

TryThis:

•  Anaerosolcancontails400.mLofcompressedgas

at5.20atm.Whenallofthegasissprayedintoa

largeplasLcbag,thebaginflatestoavolumeof

2.14L.WhatisthepressureofgasintheplasLc

bag?Assumeaconstanttemperature.

Note:

•  Youmayberequiredtouseeitherformofthe

equaLonforBoyle’sLaw

•  PV=k•  P1V1=P2V2

CalculaLngk•  Inastudytoseehowcloselygaseousammonia

obeysBoyle’slaw,severalvolumemeasurements

weremadeatvariouspressures,using1.0moleof

NH3gasatatemperatureof0°C

– Usingtheresultslistedbelow,calculatetheBoyle’slawconstantforNH

3atthevariouspressures

CalculaLngk•  Usingtheresultslistedbelow,calculatetheBoyle’slawconstantforNH

3atthevariouspressures

•  Approach:•  Calculatethevalueofk(inL.atm)foreachtrial.

CalculaLngk•  Note:AlthoughdeviaLonsfromtrueBoyle’slaw

behaviorarequitesmallattheselowpressures,the

valueofkchangesregularlyinonedirecLonasthepressureisincreased.

•  Tocalculatetheidealvalueofk,youwouldplotPVversusP,andextrapolatebacktozeropressure

(wheregasesbehavemostideally).

CalculaLngk– Valueofkobtainedby

this

extrapolaLon

is22.41L·atm

Charles’sLaw

JacquesCharles(1746-1823)

•  FrenchPhysicist•  PartofascienLficballoonflightonDec.1,1783–was

oneofthreepassengersin

thesecondballoonascension

thatcarriedhumans

•  Thisishowhisinterestingasesstarted

•  Itwasahydrogenfilledballoon–goodthingthey

werecareful!

Figure5.8-PlotsofVversusT(°C)forSeveralGases

Charles’sLaw

• WhenPisheldconstant,Tisdirectly

proporLonaltoV

Charles Law • Gas law problems involving temperature will always require that the temperature be in Kelvin.

• Reason? There will never be a zero volume, since we have never reached absolute zero.

Kelvin = °C + 273 °C = Kelvin - 273 and

Charles’sLawEx1/

•  Aballooninflatedinaroomat24°Chasavolumeof

4.00L.Theballoonisthenheatedtoatemperature

of58°C.Whatisthenewvolumeifthepressure

remainsconstant?

•  SoluLon•  First,listyourknownvalues.•  T

1=

•  T2=

•  V1=

•  V2=

Charles’sLawEx1/




remainsconstant?

•  SoluLon•  Second,writeyourequaLon.•  T

1=

•  T2=

•  V1=

•  V2=

Charles’sLawEx1/




remainsconstant?

•  SoluLon•  Third,isolateandsolve.•  T

1=

•  T2=

•  V1=

•  V2=

Gay-Lussac’sLaw

JosephLouisGay-Lussac(1778–1850)

•  Frenchchemistand

physicist

•  KnownforhisstudiesonthephysicalproperLesof

gases.

•  In1804hemadeballoon

ascensionstostudy

magneLcforcesandto

observethecomposiLon

andtemperatureoftheair

atdifferentalLtudes.

Gay-Lussac’sLaw

• WhenVisheldconstant,Pisdirectly

proporLonaltoT

Gay-Lussac’sLawEx/

•  Asampleofnitrogengashasapressureof

6.58kPaat539K.Ifthevolumedoesnot

change,whatwillthepressurebeat211K?

CombinedGasLaw

CombinedGasLaw

• Whenonlynisconstant,wecanrelateP,T,andV.

CombinedGasLawEx/

•  Thevolumeofagas-filledballoonis30.0Lat

313Kand153kPapressure.Whatwouldthe

volumebeatstandardtemperatureand

pressure(STP)?

Avogadro’sLaw

Avogadro’sLaw

•  GivenbyItalianchemistAvogadrowhopostulated

thatequalvolumesofgasesatthesame

temperatureandpressurecontainthesame

numberofparLcles

•  Foragasatconstantpressureandtemperature,the

volumeisdirectlyproporLonaltothenumberof

molesofgas

– Obeyedcloselybygasesatlowpressures•  StatedmathemaLcallyas

– V-Volumeofgas

– n-NumberofmolesofgasparLcles

– k-ProporLonalityconstant

Avogadro’sLaw

Avogadro’sLawEx/

•  Supposewehavea12.2-Lsamplecontaining0.50

moleofoxygengas(O2)atapressureof1atmand

atemperatureof25°C

–  IfallthisO2wereconvertedtoozone(O

3)atthesame

temperatureandpressure,whatwouldbethevolumeof

theozone?

Avogadro’sLawEx/



atemperatureof25°C


3)atthesame


theozone?

•  n1=0.50molO

2

•  n2=?molO

3

•  V1=12.2LO

2

•  V2=?LO

3

Avogadro’sLawEx/



atemperatureof25°C


3)atthesame


theozone?

• WeneedtoknowhowmanymolesofO3areproducedby0.50

molO2

•  OurbalancedequaLonis3O2(g)à2O

3(g)

•  UsethemoleraLotocalculatethemolesofO3formed

Avogadro’sLawEx/



atemperatureof25°C


3)atthesame


theozone?

•  n1=0.50molO

2

•  n2=0.33molO

3

•  V1=12.2LO

2

•  V2=?LO

3

SampleQuesLon•  Eachoftheballoonsholds1.0Lofdifferentgases

– Allfourareat25°C,andeachcontainsthe

samenumberofmolecules

– Ofthefollowing,whichwouldalsohavetobethesame

foreachballoon(obviouslynottheircolor)?

a.  TheirdensiLes

b.  Theirmasses

c.  Theirbuoyancies

d.  Theirpressures

SampleQuesLon

•  Acylinderisfi]edwithamovablepiston

– PressureinsidethecylinderisPi,andthevolumeisV

i

– Whatisthenewpressureinthesystemwhenthepiston

decreasesthevolumeofthecylinderbyhalf?

a.  ¼Pi

b.  ½Pi

c.  2Pi

d.  4Pi

e.  Noneofthese

CW

1.  Ch.5Packet

78

ap chemistry day 16 - ms. flemingflemingapchem.weebly.com/.../ap_chem_week_7_ch_5_a_.pdf · 2020....

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