CHEMI CALKI NETI CS:THEI ODI NECLOCKREACTI ON ______________________________________________________________________________
ABSTRACT Thi spaperi sas t udyt of or m ani deaofhowc er t ai ne xper i ment al f ac t or saff ec tt her at esofr eac t i ons . Th ee x p er i me ntc o nd uc t e dd emo ns t r a t e dh ow t h et e mp mp er a t u r e ,t h ec o nc e nt r a t i o na nd t h ea dd i t i o no fa c at al y s taff ec tt her at eofar eac t i on.Thr ought hepr epar at i onofdi ff er entr unswi t hv ar y i ngc onc ent r at i onsof 2r eac t ant swi t hac ons t antc onc ent r at i onof SO3 an dt heus eofas t ar c hi ndi c at orasabas i sf ort hee ndof 2 2− t her eac t i on,t hec hemi c al k i net i c sbehi ndt her eac t i onof SO8 andI we r eo bs e r v e d. 2 Thedi ff er entr unswer et i med t o de t er mi ne t he r at ec ons t ant ,t he r eac t i on r at e,t heor dero ft he r eac t i onan dt h er at el a w.Fr om t h er es ul t sobt ai nedi twasc onc l udedt hatt her eac t i o nf ol l o wedt hes ec ond or derr at el aw,wi t hbot ht hes odi um t hi os ul f at eandi odi deha vi ngfi r s tor der .Ther at eofr eac t i onwasal s o f oundt obedi r ec t l yaff ec t edbyt emper at ur e;ahi ghert emper at ur er es ul t edi naf as t err eac t i onr at e,andt he addi t i onofac at al y s ti nc r eas edt her at eofr eac t i on.
______________________________________________________________________________
Reagent
Concent r at i on
Po t as s i um I odi de( KI )
0 . 2 M
Po t a ss i u m Ch l o r i d e( KCl )
0 . 2 M
Po t as s i um Per s ul f at e ( K2S2O8)
0 . 1 M
Po t as si um Sul f at e( K2SO4)
0 . 1 M
So di u m Th i os ul f a t e ( Na2S2O3)
Chemi s t r ydeal swi t ht hepr e di c t i onandt he mani pul at i onofc hemi c al r eac t i ons ,andt her at eof t her eac t i onpl ay sas i gni fi cantr ol ei nt hi spr ac t i c e. Ther ear er eac t i onst hatc anhappeni nl es st hana s ec ond,whi l et her ear eot her st hatt ak eal ong per i odoft i me. Chemi c al k i net i c si st hebr anc hof c h emi s t r yt h ati sc on ce r n edwi t ht h eme ch an i s ms andr at esofc hemi c al r eac t i ons .Thedes cr i pt i onof wha th ap pe nst oe ac hmo l e cu l eo nade t ai l e dl e v el i st h eme c ha ni s mo fach emi c al r e ac t i o n.Th e me as u r e me nto far e ac t i o nss p e edi sk n o wnast h e r at eofr eac t i on.Ther at eofac hemi c al r eac t i oni s me as ur edb yh owf a s tt her e ac t a nt sdi s a pp ea r ,o r byhowf as tt hepr oduc t sar ecr eat ed[ 1] .
4. 0mM
0 . 1 M
Copper( I I )Sul f at e( CuSO4) St ar c hSol ut i on
1% w/ v
Theconc ent r at i onsoft her eac t ant swer e v ar i edf ore ac hr unaspr es ent e di nt abl e2.The v ar i edamounto ft hesol ut i onswer edonei nor der t odet er mi net heeff ec toft hec onc ent r at i onoft he r eac t ant st ot her at eofr eac t i on.
T abl e2.Thev ol umesoft her eac t ant sf ort he di ffer entr uns BEAKERA RUN
KI
BEAKERB
KCl K2S2O8 K2SO4 Na2S2O3
( mL) ( mL)
( mL)
( mL)
I NTRODUCTI ON
( mL)
1
10
0
5
5
5
2
5
5
5
5
5
3
2. 5
7. 5
5
5
5
4
5
5
7. 5
2. 5
5
5
5
5
10
0
5
Thes t udyoft her at eofac hemi c al r eac t i on oc cur sandt hef ac t or st hataffec tt hi sr at e. Re ac t i on sde pe ndont h ec he mi c al n at u r eoft h e r eac t ant san dt her at esofeac hr eac t i onar euni que gi v enas etofc ondi t i ons .Ther ear ef ourf ac t or st hat c ani nfl uenc et her at eofar eac t i ono nei st het he c onc ent r at i onandphy s i c al s t at esoft her eac t ant s , ano t heri st het emper at ur eoft hesy s t em a ndt he ot heri st hepr es enc eofacat al y s t .Asdi s c us sedby t hec ol l i s i ont heor y ,mol ec ul esoft her eac t ant s s houl dc ol l i deandmi xi nor dert or eac t . Th er at el a wi samat he ma t i c al e qu at i o n t hati dent i fi est her eac t i on’spr o gr e ss .Th ee qu at i o n r el at est her at eoft her eac t i ont ot her at ec ons t ant ( k )a ndt hec onc ent r at i onoft her eac t ant sr ai s edt o t hei rr eac t i onor der s . Th eI o di n eCl o c kRe ac t i o nEx p er i me nt ai mst odet er mi nehowt heconc ent r at i on,t he t emper at ur eandt headdi t i onofacat al y s teff ec t s t her at esofr eac t i onus i ngt her at esofdi ffer entr uns ofanI odi neandper s ul f at er eac t i onmi x t ur e. Thee xper i menti nc l udest hepr epar at i onof t hef ol l owi ngs ol ut i onsi nT abl e1.
ForSe t1al l r unswer epr epar ed.Ei ght dr opsoft hest ar c hs ol ut i onwer eaddedt obeak erB andt hesol ut i onsi nbeak erAwer epour edi nt o beak erBmar k i ngt hes t ar toft her eac t i onandt he
T abl e1.Thec onc ent r at i onoft her eagent s used
TheI odi nei sf or meds l owl yunt i l t he t hi os ul f at ei oni sus edup.Whent hec ol oroft he s ol ut i onc hangesi nt oabl uec ompl e xi ti st her es ul t oft hec ompl et ec ons umpt i onoft het hi os ul f at ei on ( Equat i on3) .Themomentt hatt hesol ut i ont ur ned i n t oab l uec omp l e xt het i me rwass t op pe d.
I t ar c h→ b l u ec o mp l e x( 3 ) 2( aq)+s Re ac hi n gt heb l u ec omp l e xp oi n to ft h e r eac t i ondependsont hec onc ent r at i onoft he r eac t ant sandt her at esoft het wor eac t i ons .I ft her e i sany t hi ngt hatwi l l s peedupt hefi r s tr eac t i ont hen t heov er al l r eac t i onwi l l al s os peedup.Ther at eof r eac t i onwoul dnotbes i gni fi canti ft hebl uec ompl e x di dnotappearori ft her eac t i ont ur nedbl ueas s oona st her eac t ant swer emi x ed.Thet hi os ul f at e i onsr egul at et her at eatwhi c hwoul dr eac tt ot he s t ar c hs ol ut i on,t her ef or et her at eofr eac t i on dependsoni t[ 3] . I nor dert oobs er v et heendoft her eac t i on t hec onc ent r at i onoft het hi os ul f at emus tbel ower t hant hec onc ent r at i onoft heper s ul f at eandi odi de i ons .Ot herwi s e,i ft het hi os ul f at ehadagr eat er c on ce nt r at i o nt h ep er s ul f a t ewo ul dbec on sume d fi r s tan dt hec hang ei nc ol orwo ul dno tb ev i s i bl e [ 4] . Ther e ac t i oni sde pe nd en tont he t hi os ul f at ei on,t her ef or et her at eoft her eac t i on ma ybec omp ut e du s i n gt h er a t eoft h e c ons umpt i onoft het hi os ul f at e( Equat i on4) .
r at e=S2O32-] ( 4 ) ∆[ 2 ∆t Theneg at i v es i gni nt hee quat i oni sus ed bec aus et het hi os ul f at ei oni sus edupandt he c onc ent r at i onwi l l ha v eaneg at i v ec ha ngegi v i n g t her at eapos i t i v ev al ue.Thet i mei sdoubl ed bec aus eoft hec oeff ec i entoft hi os ul f at ei nEquat i on 2.[ 5] Al t hough,t her at eoft her eac t i onswer e det er mi nednotus i ngt her at el aw.I ns t eadus i ngt he r ec i pr oc al oft het i meel aps edwhent hebl ue mi x t u r ewa sf o r me db ec a us ei two ul dp r o du c et h e s ameamou ntofI 2ov ert het i mea ndi sdi r ec t l y pr opor t i onal t ot her at eofr eac t i on.
r ec or di ngoft her eac t i on.Thes t ar c hs ol ut i onmi x ed wi t ht heI odi net of or mt hebl uec ompl e xi ndi c at i ng t ha tt h eI od i n ewa sf o r me dan dma r k i n gt h ee ndof t her eac t i on. Fors et2t heobs er v at i onoft heeff ec tof t emper at ur eont her at eofr eac t i o nwast es t ed.T wo s et sofRun2( i nt abl e1)wer es etup.Thi st i met he env i r onmentoft hes ol ut i onswer ei ndi ff er ent t e mp er a t u r e s .On es e to ft h es e c on dr u nwa s pl ac edi nani c ebat hwhi l et heo t hers etwas h ea t e d;t h es e t u psha dt or e ac ht h et e mp er a t ur eo f 4℃ and50℃ r es pec t i v el y .Theaddi t i onoft he s t ar c handt hemi x i ngoft hes ol ut i onsi ndi c at edt he s t ar toft her eac t i on,andt h ebl uec ompl e xf or med ma r k e dt h ee nd . Thi se xper i mentd ab bl edi nt heeff ec to fa c at al y stt ot her at eofr eac t i on.Ac at al y stl ower st he ac t i v at i onener gyoft her eac t i on.Theac t i v at i on e ne r g yi st h emi n i mu ma mo un to fe ne r g yr e qu i r e d f ort her eac t i ont ot ak epl ac e[ 2] .T oobs er v et he e ffec to fac at al y s t1 Mo ft h ec at a l y s t ,Cu SO4 ,was a dd edf o rat h i r ds etofRun2wa spr e pa r e d.Th e r e ac t i o nwa sr ec o r de da st h ec a t a l y s twasa dd ed a ndt h ec o n t e nt so fBe ak e rAa ndBwe r emi x e d , a ndt h eb l u ec o mp l e xt h atf o r me dma r k e dt h ee nd oft her eac t i on.
RESUL TSANDDI SCUSSI ON Th eI o di n eCl oc kr e ac t i o nr e co r dsho wl o ng i tt ak esf orafi xedamountoft het hi os ul f at ei onst o b ec on su me d.I nt h er e ac t i o nt he r ea r et wo pr oc es s essi mul t an eo us l yoc c ur r i ng.Thefi r s t pr oc es si sas l owr eac t i ont hatpr oduc est hei odi ne ( Equat i on1) . S2O82-(aq) + 2I SO42- ( 1) ( a q) → I 2( a q) + 2
Th eI o di n ep r o du c edi sn ev e rs e en bec aus ei ti si mmedi at el yus edu pi nav er yf as t pr oc es st hatr educ esi tbac ki nt ot hec ol our l es s i odi dei on( Equat i on2) . I S2O32-(aq) → S4O62-(aq) + 2I 2) 2( a q)+ 2 ( a q) (
c onc ent r at i onoft her eac t ant sandr ai s edt ot hei r r eac t i onor der s .[ 6]Whi c hl ook sl i k et hi s 2Ra t e=k[2 8
SO ] [ I ]
( 5)
Re ac t i o no r d er ya l s obede t e r mi n e ’sma gr aphi c al l yt hr oughpl ot t i ngofl n( r at e)v s.l n ( c onc ent r at i onoft her eac t ant s ) . Fi gur e1i st he g r a phoft h eo bt a i n ede qu at i o ny=0 . 31 8x+1 . 4 43 2 andl i near i t yval ueofR =0. 9 96 6.Th ed et e r mi n ed v al ueoft hes l opei st her eac t i onor derof 22 8
SO t ob e1 .
T abl e3 .Eff ec toft heConc ent r at i onont her at e ofr eac t i on S2O82- I M M
-
S2O32M
Rx n Ra t e ,Ms 1 t i me,s
1
0. 033
0. 2 1. 33x 10-3
2
0. 033
0. 2 1. 33x 10
3
0. 033 0. 05 1. 33x 10
4
0. 033
0. 1 1. 33x 10
5
0. 033
0. 1 1. 33x 10
3
44. 63 2. 2x 10
3
1 0 1 . 29 . 9 x1 0 4
3
25. 08 4. 0x 10
3
18. 83 5. 3x 10
2-
Fi gur e1. S2O8 ]andt her at e Ther el at i ons hi pof[
l nr a t e
Fi gur e2i st hegr ap hobt ai nedf r om t he equ at i o ny=2. 189x+1. 964wi t hal i near i t yv al u eof 2 R =0. 9952.Thes l opeoft hel i nei st her eac t i on or derofI -whi c hi sappr o xi mat el yequal t o1.
27 . 83 3. 5X10-2 2
3
2
2
I ns et1,t hec onc ent r at i onofper s ul f at ew
.
1. 2
Fi gur e2. ]andt her at e Ther el at i ons hi pof[ I -
0. 8
l n[ S2O82] l nr a t e
0. 4
Bas edont h ev a l ue sob t a i ne df r o mt h e gr aphst her at el a wc anbees t abl i s hedas 2-1
1
S2O8 ][ I ] Ra t e=k[
SUMMARYANDCONCLUSI ONS Th eI o di n eCl o c kRe ac t i o nwa san ex per i mentt hatt es t edt hr eef ac t or st hataffec tt he r at eofr eac t i on,mor es pec i fi cal l y :t he c onc ent r at i on,t h et emper at ur eandt heus eofa c at al y s t .
0 asc ons t antf orr uns1,2and3whi l et he c onc ent r at i onofi odi dewast hec ons t antf orr uns2, 4a nd5.Thefi na lc o nc e nt r at i ono ft h ei o nswer e c al c ul at edf r om t hemol arc onc ent r at i onand v ol umesofeac hs ol ut i o ni ne v er yr un.Us i ngt he i ni t i al r at emet hodt her eac t i onor der sofper s ul f at e andi odi dewer ecal c ul at ed. Ther eac t i onor derc al c ul at edf orper s ul f at e wa sc l o s et o1a ndf o ri o di d ewa s1ma k i n gt h e ov er al l r eac t i onor dert obe2.Ther at el awi s e xpr es s edast her at ec ons t antmul t i pl i edbyt he
Theval u est ha tar eobt ai ne d
2. 5
2
1. 5
l n[ I ]
1
0. 5
0 2 . 1 8 9 ma yv ar yde pe nd i n go nt h ef a c t o r st h atma yaff e c t t her e ac t i on.Forone,ani nac c ur at et i merma ybea l i abl es our c ef orer r or ,ot herf ac t or scoul dbet he t h er mo me t e rwh i c hc ou l dc ha ng et h et e mp er a t u r e t hati sr ec or ded. Ther e su l t sob t a i n edan dp r e se nt e d t hr ought hi sex per i mentar eno tt oof arofff r om
Var y i ngt hec onc ent r at i onoft her eac t ant s ma ya ffec tt h ea v er a ger e ac t i o nt i mea swe l l a st h e r at eoft her eac t i on.I nc r eas i ngt het emper at ur e i nc r eas esr eac t i onr at esbec aus eoft h e di s pr opor t i onat el yl ar gei nc r eas ei nt henumberof hi ghf r equenc yc ol l i s i ons .I ti sonl yt hes ec ol l i s i ons i ft heypos ses st heac t i v at i onener gyf ort he r eac t i ont hatwi l l r es ul ti nar eac t i on.Theaddi t i onof ac at al y stl ower st heac t i v at i onener gyoft he r eac t i onal l owi ngi tt opr oc eedf as t er .
o t h ere x per i men t a lfi n di ng s.Th edi ff er e nc e sma y b ea cc ou nt e df o ra ser r o r sandmi s r e adi n gsofd at a . [ 3][ 4]Har r i s ,D. C.2011.Quant i t at i v eChemi c al An al y s i s :Ei g htEdi t i on .Ne w Yor k :W. H.Fr e ema n Company .347. [ 5][ 6]Upad hy a y ,S. K.2006.Chemi c al Ki ne t i c sand Re a c t i o nDy n a mi c s . Ne wY or k : An a ma y a Publ i s her s .26
REFERENCES [ 1 ]Cha ng ,R.20 07 .Ch emi s t r y :Ni n t hEd i t i o n.Ne w Yo r k :Mc Gr a w Hi l l .5 495 53 . [ 2]" CHEM 1112. ” Ki net i c soft hePer s ul f at e– i od i d eCl oc kRe ac t i o n.Web . .
APPENDI XA-Li stofTabl es
onc ent r at i onoft her eagent sus ed T abl e1.Thec ol umesoft her eac t ant sf ort hedi ffer entr uns T abl e2.Thev T a bl e3. Effec toft hec onc ent r at i onont her at eofr eac t i on
APPENDI XB-Li stofFi gur es
Fi gur e1. Ther el at i ons hi pof[ S2O82-]andt her at e
APPENDI XB-SAMPLECALCULATI ONS
Ra t eOr d er s m n Rat e=k[ S2O82-] [ I ]
m n 3. 5X10-2 = k ( 0. 033) ( 0. 2) m n 2. 2x 10-2 k ( 0. 033) ( 0. 1)
m 1 4. 0X10-2 = k ( 0. 033) ( 0. 1) m 1 2. 2x 10-2 k ( 0. 033) ( 0. 1)
n=0 . 7 95 5
m =1
Rat eConst ant
Run2:0. 033M per s ul f at e0. 1 Mi o di d e k= 2
r at e = 2. 2x 10k=6. 6666667 [ I ] [ S2O82-] ( 0. 033)
( 0. 1)
Sol ut i onPr epar at i ons For500mL0. 2M KI 500mLx 1L x0. 2M x 166g =16. 6g 1000mL 1mol
REFERENCES
