CHAPTER 13 j
Rates of Reaction
j j
■ SOLUTIONSjTOjEXERCISES
Notejonjsignificantjfigures:jIfjthejfinaljanswerjtojajsolutionjneedsjtojbejroundedjoff,jitjisjgivenjfirstjwithjonej
nonsignificantjfigure,jandjthejlastjsignificantjfigurejisjunderlined.jThejfinaljanswerjisjthenjroundedjtojthejcor
rectjnumberjofjsignificantjfigures.jInjmultistepjproblems,jintermediatejanswersjarejgivenjwithjatjleastjonejn
onsignificantjfigure;jhowever,jonlyjthejfinaljanswerjhasjbeenjroundedjoff.
13.1. RatejofjformationjofjNO2Fj=j[NO2F]/t.jRatejofjreactionjofjNO2j =j−[NO2]/t.jDividejeachjra
tejbyjthejcoefficientjofjthejcorrespondingjsubstancejinjthejequation:
½j[NO2jF]j =j−½j[NO2j]j;jorj [NO2jF]j =j−j [NO2j]
t t t t
[I-j]j [0.00101jMj−j0.00169jM]
13.2. Ratej=j− =j− =j1.13jj10−4j=j1.1jj10−4jM/s
t 8.00jsj−j2.00js
13.3. ThejorderjwithjrespectjtojCOjisjzerojandjwithjrespectjtojNO2j isj2.jThejoveralljorderjisj2,jthejsumjofjt
hejexponentsjinjthejratejlaw.
13.4. ByjcomparingjExperimentsj1jandj2,jyoujseejthejratejisjquadrupledjwhenjthej[NO2]jisjdoubled.jTh
us,jthejreactionjisjsecondjorderjinjNO2,jandjthejratejlawjis
Ratej=jk[NO2]2
Thejratejconstantjmayjbejfoundjbyjsubstitutingjexperimentaljvaluesjintojthejrate-
lawjexpression.jBasedjonjvaluesjfromjExperimentj1,
kj= 7.1j j 10−5j mol/(Lj•js)j
ratej[ =j (0.010jmol/L)2
=j0.710j=j0.71jL/(mol•s)
NOj ]22
13.5. a. Forj[N2O5]jafterj6.00jj102js,jusejthejfirst-
orderjratejlaw,jandjsolvejforjthejconcentrationjatjtimejt:
ln
[N2O5j]tj [1.6 =j−(4.80jj10 j/s)(6.00jj10 js)j=j−0.2880
−4 2
5j j 10 j M]
−2
Takejthejantilogjofjbothjsidesjtojget
[N2O5j]tj [1.6
=je−0.2880j=j0.74976
5j j 10−2j M]
Hence,
[N2O5]tj =j1.65jj10−2jMjj0.74976j=j0.01237j=j0.0124jmol/L
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, Chapterj 13:j Ratesj ofj Reaction 453
b. Substitutejthejvaluesjintojthejratejequationjtojget
10.0%
lnj =j−(4.80jj10−4/s)jjt
100.0%
Takingjthejlogjonjthejleftjsidejgivesjln(0.100)j=j−2.30258.jHence,
−2.30258j=j−(4.80jj10−4j/s)jjt
or,
2.30258
tj= =j4797j=j4.80jj103jsj(80.0jmin)
4.80j j 10−4/s
13.6. Substitutejkj=j9.2/sjintojthejequationjrelatingjkjandjt½.jt½
0.693j 0.693j
j =j =j =j0.0753j=j0.075js
k 9.2/s
Byjdefinition,jthejhalf-
lifejisjthejamountjofjtimejitjtakesjtojdecreasejthejamountjofjsubstancejpresentjbyjone-
half.jThus,jitjtakesj0.0753jsjforjthejconcentrationjtojdecreasejbyj50%jandjanotherj0.0753jsjforjthejco
ncentrationjtojdecreasejbyj50%jofjthejremainingj50%j(toj25%jleft),jforjajtotaljofj0.1506,jorj0.151js.
13.7. SolvejforjEaj byjsubstitutingjthejgivenjvaluesjintojthejtwo-temperaturejArrheniusjequation:
lnj2.14j j 10
−2
j E 1 1
= a −
1.05j j 10−3
j
8.31jJ/(molj•jK)j 759jK 836jKj
Ea
3.0146j= (1.21jj10−4j/K)
8.31jJ/(molj•jK)
Eaj = 3.0146j 8.31jJ/mol =j2.06jj105j=j2.1jj105jJ/mol
1.21j j 10−4
Solvejforjthejratejconstant,jk2,jatj865jKjbyjusingjthejsamejequationjandjusing
Eaj =j2.06jj105jJ/mol:
1 j
ln k2 2.06j j 105j J/molj 1 − =j0.994
=j
j
8.31jJ/(molj•jK) 836jK 865jKj
j j j
Takingjantilogarithms,
k2
=je0.994j=j2.7
j j j
k2j =j2.7jj(2.14jj10−2)/(M½•s)j=j5.8jj10−2j=j6jj10−2j(M½•s)
13.8. Thejnetjchemicaljequationjisjthejoveralljsumjofjthejtwojelementaryjreactions:jH
2O2j +jI
−
→j H2Oj+jIO−
H2O2j +jIO− →j H2Oj+jO2j +jI−
2H2O2 →j 2H2Oj+jO2
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, 454 Chapterj 13:j Ratesj ofj Reaction
ThejIO−jisjanjintermediatejbecausejitjisjproducedjinjStepj1jandjlaterjconsumedjinjStepj2;jI−jisjajcatal
ystjbecausejitjisjtemporarilyjusedjinjStepj1jbutjthenjregeneratedjinjStepj2.jNeitherjappearsjinjthejnetje
quation.
13.9. Thejreactionjisjbimolecularjbecausejitjisjanjelementaryjreactionjthatjinvolvesjtwojmolecules.
13.10. ForjNO2j +jNO2j →jN2O4,jthejratejlawjisj
Ratej=jk[NO2]2
(Thejratejmustjbejproportionaljtojthejconcentrationjofjbothjreactantjmolecules.)
13.11. Thejfirstjstepjisjthejslow,jrate-
determiningjstep.jTherefore,jthejratejlawjpredictedjbyjthejmechanismjgivenjis
Ratej=jk1j [H2O2][I−]
13.12. Accordingjtojthejrate-
determiningj(slow)jstep,jthejratejlawjisjRatej=jk2[NO3][
NO]
EliminatejNO3j fromjthejratejlawjbyjlookingjatjthejfirstjstep,jwhichjisjfastjandjreachesjequilibrium.j
Atjequilibrium,jthejforwardjratejandjthejreversejratejarejequal.
k1[NO][O2]j=jk−1[NO3]
Therefore,j[NO3]j=j(k1/k−1)[NO][O2],jso
k2jk1j
Ratej= [NO]2[O2]j=jk[NO]2[O2]
k-1
wherejk2(k1/k−1)jhasjbeenjreplacedjbyjk,jwhichjrepresentsjthejexperimentallyjobservedjratejconstant.
■ ANSWERSjTOjCONCEPTjCHECKS
13.1. a. SincejthejslopejisjsteeperjatjpointjA,jpointjAjmustjbejajfasterjinstantaneousjrate.
b. Sincejthejcurvejisjnotjajflatjline,jthejratejofjreactionjmustjbejconstantlyjchangingjoverjtime.jTh
erefore,jthejratejforjthejreactionjcannotjbejconstantjatjalljpointsjinjtime.
13.2. a.
Keepingjinjmindjthatjalljreactantjspeciesjmustjbejpresentjinjsomejconcentrationjforjajre
actionjtojoccur,jthejreactionjwithj[Q]j=j0jisjthejslowestjbecausejnojreactionjoccurs.jThejotherj
twojreactionsjarejequaljinjratejbecausejthejreactionjisjzerojorderjwithjrespectjtoj[Q];jasjlongjas
jtherejisjsomejamountjofjQjpresent,jthejreactionjratejdependsjonjthej[R],jwhichjisjconstantjinjt
hisjcase.
b. Sincej[Q]oj=j1,jyoujcanjrewritejthejratejlawjasjfollows:jRatej=jk[R]2.
13.3. a.
AjpossiblejratejlawjisjRatejofjagingj=j(diet)w(exercise)x(sex)y(occupation)z.jYourjratej
lawjprobablyjwilljbejdifferent;jhowever,jthejgeneraljformjshouldjbejthejsame.
b. Youjwilljneedjajsamplejofjpeoplejwhojhavejalljthejfactorsjthejsamejexceptjone.jForjexamp
le,jusingjthejequationjgivenjinjpartja,jyoujcouldjdeterminejthejeffectjofjdietjifjyoujhadjajsa
mplejofjpeoplejwhojwerejthejsamejsex,jexercisedjthejsamejamount,jandjhadjthe
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, Chapterj 13:j Ratesj ofj Reaction 455
samejoccupation.jYoujwouldjneedjtojisolatejeachjfactorjinjthisjfashionjtojdeterminejthejexpon
entjonjeachjfactor.
c. Thejexponentjonjthejsmokingjfactorjwouldjbej2jsincejyoujseejajfourfoldjratejincrease:j[2
]2j=j4.
13.4. Thejhalf-lifejofjajfirst-orderjreactionjisjconstantjoverjthejcoursejofjthejreaction.jThejhalf-
lifejofjajsecond-
orderjreactionjdependsjonjthejinitialjconcentrationjandjbecomesjlongerjasjtimejelapses.jThus,jthejre
actionjmustjbejsecondjorderjbecausejthejhalf-lifejincreasesjfromj20jsjtoj40jsjafterjtimejhasjelapsed.
13.5. a. Sincejthej“hump”jisjlarger,jthejAj+jBjreactionjhasjajhigherjactivationjenergy.
b. Sincejthejactivationjenergyjisjlower,jthejEj+jFjreactionjwouldjhavejthejlargerjratejconstant.jKe
epjinjmindjthejinversejrelationshipjbetweenjthejactivationjenergy,jEa,jandjthejratejconstant,jk.
c. Since,jinjbothjcases,jenergyjperjmolejofjthejreactantsjisjgreaterjthanjthatjofjthejproducts,jbo
thjreactionsjarejexothermic.
13.6. a.
Herjfindingjshouldjincreasejthejratejsincejthejactivationjenergy,jEa,jisjinverselyjrelate
djtojthejratejconstant,jk;jajdecreasejinjEaj resultsjinjanjincreasejinjthejvaluejofjk.
b. Thisjisjpossiblejbecausejthejratejlawjdoesjnotjhavejtojreflectjthejoveralljstoichiometryjofjth
ejreaction.
c. No.jSincejthejratejlawjisjbasedjonjthejslowjstepjofjthejmechanism,jitjshouldjbejRatej=
k[Y]2.
■ ANSWERSjTOjSELF-ASSESSMENTjANDjREVIEWjQUESTIONS
13.1. Thejfourjvariablesjthatjcanjaffectjratejarej(1)jthejconcentrationsjofjthejreactants,jalthoughjinjsomejca
sesjajparticularjreactant'sjconcentrationjdoesjnotjaffectjthejrate;j(2)jthejpresencejandjconcentrationjo
fjajcatalyst;j(3)jthejtemperaturejofjthejreaction;jandj(4)jthejsurfacejareajofjanyjsolidjreactantjorjsolidj
catalyst.
13.2. ThejratejofjreactionjofjHBrjcanjbejdefinedjasjthejdecreasejinjHBrjconcentrationj(orjthejincreasejinj
Br2j productjformed)joverjthejtimejinterval,jt:
[HBr]j [Br2j ]j [HBr]j [Br2j]
Ratej =j−¼j =j ½j orj −j =j 2j
t t t t
13.3. Twojphysicaljpropertiesjusedjtojdeterminejthejratejarejcolor,jorjabsorptionjofjelectromagneticjradiat
ion,jandjpressure.jIfjajreactantjorjproductjisjcolored,jorjabsorbsjajdifferentjtypejofjelectromagneticjra
diationjthanjthejotherjspecies,jthenjmeasurementjofjthejchangejinjcolorj(changejinjabsorptionjofjelect
romagneticjradiation)jmayjbejusedjtojdeterminejthejrate.jIfjajgasjreactionjinvolvesjajchangejinjthejnu
mberjofjgaseousjmolecules,jmeasurementjofjthejpressurejchangejmayjbejusedjtojdeterminejthejrate.
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
Rates of Reaction
j j
■ SOLUTIONSjTOjEXERCISES
Notejonjsignificantjfigures:jIfjthejfinaljanswerjtojajsolutionjneedsjtojbejroundedjoff,jitjisjgivenjfirstjwithjonej
nonsignificantjfigure,jandjthejlastjsignificantjfigurejisjunderlined.jThejfinaljanswerjisjthenjroundedjtojthejcor
rectjnumberjofjsignificantjfigures.jInjmultistepjproblems,jintermediatejanswersjarejgivenjwithjatjleastjonejn
onsignificantjfigure;jhowever,jonlyjthejfinaljanswerjhasjbeenjroundedjoff.
13.1. RatejofjformationjofjNO2Fj=j[NO2F]/t.jRatejofjreactionjofjNO2j =j−[NO2]/t.jDividejeachjra
tejbyjthejcoefficientjofjthejcorrespondingjsubstancejinjthejequation:
½j[NO2jF]j =j−½j[NO2j]j;jorj [NO2jF]j =j−j [NO2j]
t t t t
[I-j]j [0.00101jMj−j0.00169jM]
13.2. Ratej=j− =j− =j1.13jj10−4j=j1.1jj10−4jM/s
t 8.00jsj−j2.00js
13.3. ThejorderjwithjrespectjtojCOjisjzerojandjwithjrespectjtojNO2j isj2.jThejoveralljorderjisj2,jthejsumjofjt
hejexponentsjinjthejratejlaw.
13.4. ByjcomparingjExperimentsj1jandj2,jyoujseejthejratejisjquadrupledjwhenjthej[NO2]jisjdoubled.jTh
us,jthejreactionjisjsecondjorderjinjNO2,jandjthejratejlawjis
Ratej=jk[NO2]2
Thejratejconstantjmayjbejfoundjbyjsubstitutingjexperimentaljvaluesjintojthejrate-
lawjexpression.jBasedjonjvaluesjfromjExperimentj1,
kj= 7.1j j 10−5j mol/(Lj•js)j
ratej[ =j (0.010jmol/L)2
=j0.710j=j0.71jL/(mol•s)
NOj ]22
13.5. a. Forj[N2O5]jafterj6.00jj102js,jusejthejfirst-
orderjratejlaw,jandjsolvejforjthejconcentrationjatjtimejt:
ln
[N2O5j]tj [1.6 =j−(4.80jj10 j/s)(6.00jj10 js)j=j−0.2880
−4 2
5j j 10 j M]
−2
Takejthejantilogjofjbothjsidesjtojget
[N2O5j]tj [1.6
=je−0.2880j=j0.74976
5j j 10−2j M]
Hence,
[N2O5]tj =j1.65jj10−2jMjj0.74976j=j0.01237j=j0.0124jmol/L
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, Chapterj 13:j Ratesj ofj Reaction 453
b. Substitutejthejvaluesjintojthejratejequationjtojget
10.0%
lnj =j−(4.80jj10−4/s)jjt
100.0%
Takingjthejlogjonjthejleftjsidejgivesjln(0.100)j=j−2.30258.jHence,
−2.30258j=j−(4.80jj10−4j/s)jjt
or,
2.30258
tj= =j4797j=j4.80jj103jsj(80.0jmin)
4.80j j 10−4/s
13.6. Substitutejkj=j9.2/sjintojthejequationjrelatingjkjandjt½.jt½
0.693j 0.693j
j =j =j =j0.0753j=j0.075js
k 9.2/s
Byjdefinition,jthejhalf-
lifejisjthejamountjofjtimejitjtakesjtojdecreasejthejamountjofjsubstancejpresentjbyjone-
half.jThus,jitjtakesj0.0753jsjforjthejconcentrationjtojdecreasejbyj50%jandjanotherj0.0753jsjforjthejco
ncentrationjtojdecreasejbyj50%jofjthejremainingj50%j(toj25%jleft),jforjajtotaljofj0.1506,jorj0.151js.
13.7. SolvejforjEaj byjsubstitutingjthejgivenjvaluesjintojthejtwo-temperaturejArrheniusjequation:
lnj2.14j j 10
−2
j E 1 1
= a −
1.05j j 10−3
j
8.31jJ/(molj•jK)j 759jK 836jKj
Ea
3.0146j= (1.21jj10−4j/K)
8.31jJ/(molj•jK)
Eaj = 3.0146j 8.31jJ/mol =j2.06jj105j=j2.1jj105jJ/mol
1.21j j 10−4
Solvejforjthejratejconstant,jk2,jatj865jKjbyjusingjthejsamejequationjandjusing
Eaj =j2.06jj105jJ/mol:
1 j
ln k2 2.06j j 105j J/molj 1 − =j0.994
=j
j
8.31jJ/(molj•jK) 836jK 865jKj
j j j
Takingjantilogarithms,
k2
=je0.994j=j2.7
j j j
k2j =j2.7jj(2.14jj10−2)/(M½•s)j=j5.8jj10−2j=j6jj10−2j(M½•s)
13.8. Thejnetjchemicaljequationjisjthejoveralljsumjofjthejtwojelementaryjreactions:jH
2O2j +jI
−
→j H2Oj+jIO−
H2O2j +jIO− →j H2Oj+jO2j +jI−
2H2O2 →j 2H2Oj+jO2
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, 454 Chapterj 13:j Ratesj ofj Reaction
ThejIO−jisjanjintermediatejbecausejitjisjproducedjinjStepj1jandjlaterjconsumedjinjStepj2;jI−jisjajcatal
ystjbecausejitjisjtemporarilyjusedjinjStepj1jbutjthenjregeneratedjinjStepj2.jNeitherjappearsjinjthejnetje
quation.
13.9. Thejreactionjisjbimolecularjbecausejitjisjanjelementaryjreactionjthatjinvolvesjtwojmolecules.
13.10. ForjNO2j +jNO2j →jN2O4,jthejratejlawjisj
Ratej=jk[NO2]2
(Thejratejmustjbejproportionaljtojthejconcentrationjofjbothjreactantjmolecules.)
13.11. Thejfirstjstepjisjthejslow,jrate-
determiningjstep.jTherefore,jthejratejlawjpredictedjbyjthejmechanismjgivenjis
Ratej=jk1j [H2O2][I−]
13.12. Accordingjtojthejrate-
determiningj(slow)jstep,jthejratejlawjisjRatej=jk2[NO3][
NO]
EliminatejNO3j fromjthejratejlawjbyjlookingjatjthejfirstjstep,jwhichjisjfastjandjreachesjequilibrium.j
Atjequilibrium,jthejforwardjratejandjthejreversejratejarejequal.
k1[NO][O2]j=jk−1[NO3]
Therefore,j[NO3]j=j(k1/k−1)[NO][O2],jso
k2jk1j
Ratej= [NO]2[O2]j=jk[NO]2[O2]
k-1
wherejk2(k1/k−1)jhasjbeenjreplacedjbyjk,jwhichjrepresentsjthejexperimentallyjobservedjratejconstant.
■ ANSWERSjTOjCONCEPTjCHECKS
13.1. a. SincejthejslopejisjsteeperjatjpointjA,jpointjAjmustjbejajfasterjinstantaneousjrate.
b. Sincejthejcurvejisjnotjajflatjline,jthejratejofjreactionjmustjbejconstantlyjchangingjoverjtime.jTh
erefore,jthejratejforjthejreactionjcannotjbejconstantjatjalljpointsjinjtime.
13.2. a.
Keepingjinjmindjthatjalljreactantjspeciesjmustjbejpresentjinjsomejconcentrationjforjajre
actionjtojoccur,jthejreactionjwithj[Q]j=j0jisjthejslowestjbecausejnojreactionjoccurs.jThejotherj
twojreactionsjarejequaljinjratejbecausejthejreactionjisjzerojorderjwithjrespectjtoj[Q];jasjlongjas
jtherejisjsomejamountjofjQjpresent,jthejreactionjratejdependsjonjthej[R],jwhichjisjconstantjinjt
hisjcase.
b. Sincej[Q]oj=j1,jyoujcanjrewritejthejratejlawjasjfollows:jRatej=jk[R]2.
13.3. a.
AjpossiblejratejlawjisjRatejofjagingj=j(diet)w(exercise)x(sex)y(occupation)z.jYourjratej
lawjprobablyjwilljbejdifferent;jhowever,jthejgeneraljformjshouldjbejthejsame.
b. Youjwilljneedjajsamplejofjpeoplejwhojhavejalljthejfactorsjthejsamejexceptjone.jForjexamp
le,jusingjthejequationjgivenjinjpartja,jyoujcouldjdeterminejthejeffectjofjdietjifjyoujhadjajsa
mplejofjpeoplejwhojwerejthejsamejsex,jexercisedjthejsamejamount,jandjhadjthe
©j2017jCengagejLearning.jAlljRightsjReserved.jMayjnotjbejscanned,jcopiedjorjduplicated,jorjpostedjtojajpubliclyjaccessiblejwebsite,jinjwholejorjinjpart.
, Chapterj 13:j Ratesj ofj Reaction 455
samejoccupation.jYoujwouldjneedjtojisolatejeachjfactorjinjthisjfashionjtojdeterminejthejexpon
entjonjeachjfactor.
c. Thejexponentjonjthejsmokingjfactorjwouldjbej2jsincejyoujseejajfourfoldjratejincrease:j[2
]2j=j4.
13.4. Thejhalf-lifejofjajfirst-orderjreactionjisjconstantjoverjthejcoursejofjthejreaction.jThejhalf-
lifejofjajsecond-
orderjreactionjdependsjonjthejinitialjconcentrationjandjbecomesjlongerjasjtimejelapses.jThus,jthejre
actionjmustjbejsecondjorderjbecausejthejhalf-lifejincreasesjfromj20jsjtoj40jsjafterjtimejhasjelapsed.
13.5. a. Sincejthej“hump”jisjlarger,jthejAj+jBjreactionjhasjajhigherjactivationjenergy.
b. Sincejthejactivationjenergyjisjlower,jthejEj+jFjreactionjwouldjhavejthejlargerjratejconstant.jKe
epjinjmindjthejinversejrelationshipjbetweenjthejactivationjenergy,jEa,jandjthejratejconstant,jk.
c. Since,jinjbothjcases,jenergyjperjmolejofjthejreactantsjisjgreaterjthanjthatjofjthejproducts,jbo
thjreactionsjarejexothermic.
13.6. a.
Herjfindingjshouldjincreasejthejratejsincejthejactivationjenergy,jEa,jisjinverselyjrelate
djtojthejratejconstant,jk;jajdecreasejinjEaj resultsjinjanjincreasejinjthejvaluejofjk.
b. Thisjisjpossiblejbecausejthejratejlawjdoesjnotjhavejtojreflectjthejoveralljstoichiometryjofjth
ejreaction.
c. No.jSincejthejratejlawjisjbasedjonjthejslowjstepjofjthejmechanism,jitjshouldjbejRatej=
k[Y]2.
■ ANSWERSjTOjSELF-ASSESSMENTjANDjREVIEWjQUESTIONS
13.1. Thejfourjvariablesjthatjcanjaffectjratejarej(1)jthejconcentrationsjofjthejreactants,jalthoughjinjsomejca
sesjajparticularjreactant'sjconcentrationjdoesjnotjaffectjthejrate;j(2)jthejpresencejandjconcentrationjo
fjajcatalyst;j(3)jthejtemperaturejofjthejreaction;jandj(4)jthejsurfacejareajofjanyjsolidjreactantjorjsolidj
catalyst.
13.2. ThejratejofjreactionjofjHBrjcanjbejdefinedjasjthejdecreasejinjHBrjconcentrationj(orjthejincreasejinj
Br2j productjformed)joverjthejtimejinterval,jt:
[HBr]j [Br2j ]j [HBr]j [Br2j]
Ratej =j−¼j =j ½j orj −j =j 2j
t t t t
13.3. Twojphysicaljpropertiesjusedjtojdeterminejthejratejarejcolor,jorjabsorptionjofjelectromagneticjradiat
ion,jandjpressure.jIfjajreactantjorjproductjisjcolored,jorjabsorbsjajdifferentjtypejofjelectromagneticjra
diationjthanjthejotherjspecies,jthenjmeasurementjofjthejchangejinjcolorj(changejinjabsorptionjofjelect
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