chem kinetics ib questions

7/17/2019 chem kinetics ib questions

1/26

r1. Consider the following graph of ln k against for the rst order decomposition of

N2O4into NO2. Determine the activation energy in kJ mol

for this reaction.

(Total 2 marks)


2/26

2. !romine and nitrogen"##$ o%ide react according to the following e&'ation.

!r2"g$ ( 2NO"g$ ) 2NO!r"g$

*hich rate e&'ation is consistent with the e%perimental data+

[Br2] / mol dm3

[NO] / mol dm3

Rate / mol dm3

s1

,., ,., ., - ,

,.2, ,., 4., - ,

,.2, ,.4, 4., - ,

/. rate 0 k1!r221NO

!. rate 0 k1!r2 1NO2

C. rate 0 k1!r22

D. rate 0 k1NO2

(Total 1 mark)

3. *hich step is the rate3determining step of a reaction+

/. he step with the lowest activation energy

!. he nal step

C. he step with the highest activation energy

D. he rst step(Total 1 mark)


3/26


4/26

"8$ Determine the activation energy7 Ea7 for this reaction.

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(3)

"c$ he rate e%pression for this reaction is rate 0 k 1N2O2and the rate

constant is,.244 dm9mol

s

at :;,


5/26

5. he rate information 8elow was o8tained for the following reaction at aconstant temperat're.

2NO2"g$ ( >2"g$ ) 2NO2>"g$

[NO2] / mol dm3

[F2] / mol dm3

Rate / mol dm3

s1

2., - ,9

., - ,2

4., - ,4

4., - ,9

., - ,2

?., - ,4

4., - ,9

2., - ,2

. - ,9

*hat are the orders of the reaction with respect to NO2and >2+

/. NO2is rst order and >2is second order

!. NO2is second order and >2is rst order

C. NO2is rst order and >2is rst order

D. NO2is second order and >2is second order

(Total 1 mark)

6. Consider the following reaction.

2NO"g$ ( 2@2"g$ ) N2"g$ ( 2@2O"g$

/ proposed reaction mechanism isA

NO"g$ ( NO"g$ N2O2"g$ fastN2O2"g$ ( @2"g$

) N2O"g$ ( @2O"g$ slowN2O"g$ ( @2"g$

) N2"g$ ( @2O"g$ fast

*hat is the rate e%pression+

/. rate 0 k1@2 1NO2

!. rate 0 k1N2O2 1@2

C. rate 0 k1NO21@2

2

D. rate 0 k1NO21N2O2

21@2

(Total 1 mark)


6/26

7. @ydrogen and nitrogen"##$ o%ide react according to the following e&'ation.

2@2"g$ ( 2NO"g$ N2"g$ ( 2@2O"g$

/t time 0 t seconds7 the rate of the reaction is

rate 0 k1@2"g$1NO"g$

2

"i$ B%plain precisely what the s&'are 8rackets aro'nd nitrogen"##$ o%ide71NO"g$7 represent in this conte%t.

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(1)

"ii$ Ded'ce the 'nits for the rate constant k.

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(1)

(Total 2 marks)

. *hich e%perimental proced're co'ld 8e 'sed to determine the rate ofreaction for the reaction 8etween a sol'tion of co8alt chloride7 CoCl2"a&$7

and concentrated hydrochloric acid7 @Cl"a&$+

Co"@2O$2(

"a&$ ( 4Cl"a&$ CoCl4

2"a&$ ( @2O"l$

/. eas're the change in p@ in a given time

!. eas're the change in mass in a given time

C. se a colorimeter to meas're the change in colo'r in a given time

D. eas're the change in vol'me of the sol'tion in a given time(Total 1 mark)


7/26

!. 6odi'm thios'lfate sol'tion7 Na262O9"a&$7 and hydrochloric acid7 @Cl"a&$7

react spontaneo'sly to prod'ce solid s'lf'r7 6"s$7 according to the e&'ation8elow.

62O92

"a&$ ( 2@

(

"a&$ ) 6"s$ ( 6O2"a&$ ( @2O"l$

/ st'dent e%perimentally determined the rate e%pression to 8eA

rate 0 k162O92

"a&$2

*hich graph is consistent with this information+

(Total 1 mark)


8/26

1". /le% and @annah were asked to investigate the kinetics involved in theiodination of propanone.hey were given the following e&'ation 8y theirteacher.

C@9COC@9"a&$ ( #2"a&$ C@2#COC@9"a&$ ( @#"a&$

/le%Es hypothesis was that the rate will 8e aFected 8y changing theconcentrations of the propanone and the iodine7 as the reaction can happenwitho't a catalyst. @annahEs hypothesis was that as the catalyst is involvedin the reaction7 the concentrations of the propanone7 iodine and thehydrogen ions will all aFect the rate.

hey carried o't several e%periments varying the concentration of one ofthe reactants or the catalyst while keeping other concentrations andconditions the same7 and o8tained the res'lts 8elow.

#om$os%t%o& 'ol*me

o+m%,t*re /

-m3

&%t%alrate

,$er%me&t

1."" mol

dm3

#03#O#0

3(a)

ater 1."" mol

dm3

0

(a)

5.""

1"3

mol

dm3

2%&

/ mol dm

3s

1

,., ,., ,., 2,., 4.G - ,

2 ,., ;,., ,., 9,., ;.,4 - ,

9 ;., ;., ,., 2,., 2.4: - ,

4 ,., ;., ;., 2,., 2.; - ,

"a$ B%plain why they added water to the mi%t'res.

......................................................................................................................................

......................................................................................................................................

(1)

"8$ "i$ Ded'ce the order of reaction for each s'8stance and the rate


9/26

e%pression from the res'lts.

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(2)


10/26

"ii$ Comment on whether /le%Es or @annahEs hypothesis is correct.

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(1)

"c$ sing the data from B%periment 7 determine the concentration of thes'8stances 'sed and the rate constant for the reaction incl'ding its'nits.

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(3)

"d$ "i$ his reaction 'ses a catalyst. 6ketch and annotate the a%well3!oltHmann energy distri8'tion c'rve for a reaction with andwitho't a catalyst on la8elled a%es 8elow.

(3)

"ii$ Descri8e how a catalyst works.

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11/26

..................

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(1)(Total 11 marks)

11. "a$ he prod'ction of ammonia is an important ind'strial process.

N2"g$ ( 9@2"g$ 2N@9"g$

"i$ sing the average 8ond enthalpy val'es in a8le , of the Data!ooklet7 determine the standard enthalpy change for this

reaction.(3)

"ii$ he standard entropy val'es7 S7 at 2G? 5 for N2"g$7 @2"g$ and

N@9"g$ are G97 9 and G2 J5

mol

respectively. Calc'late ISO

for the reaction and with reference to the e&'ation a8ove7 e%plain

the sign of ISO.

(4)

"iii$ Calc'late IGOfor the reaction at 2G? 5.

(1)

"iv$ Descri8e and e%plain the eFect of increasing temperat're on thespontaneity of the reaction.

(2)

"8$ he reaction 'sed in the prod'ction of ammonia is an e&'ili8ri'mreaction. O'tline the characteristics of a system at e&'ili8ri'm.

(2)

"c$ Ded'ce the e&'ili8ri'm constant e%pression7 Kc7 for the prod'ction of

ammonia.(1)

"d$ "i$ ,.2, mol of N2"g$ and ,.2, mol of @2"g$ were allowed to reach

e&'ili8ri'm in a dm9closed container. /t e&'ili8ri'm the


12/26

concentration of N@9"g$ was ,.,, mol dm9

. Determine the

e&'ili8ri'm concentrations of N2"g$ and @2"g$ and calc'late the

val'e of Kc.

(3)

"ii$ redict and e%plain how increasing the temperat're will aFect theval'e of Kc.

(2)


13/26

"e$ Descri8e how increasing the press're aFects the yield of ammonia.(2)

"f$ #n practice7 typical conditions 'sed in the @a8er process are atemperat're of ;,,


14/26

13. Consider the following reaction.

NO2"g$ ( CO"g$ ) NO"g$ ( CO2"g$

/t T K 22:


15/26

15. *hat happens when the temperat're of a reaction increases+

/. he activation energy increases.

!. he rate constant increases.

C. he enthalpy change increases.

D. he order of the reaction increases.(Total 1 mark)

16. "a$ here are fo'r str'ct'ral isomers with the molec'lar form'la C4@G!r.

One of these str'ct'ral isomers e%ists as two optical isomers. Drawdiagrams to represent the three3dimensional str'ct'res of the twooptical isomers.

(2)

"8$ /ll the isomers can 8y hydrolysed with a&'eo's sodi'm hydro%idesol'tion. *hen the reaction of one of these isomers7 7 wasinvestigated the following kinetic data were o8tained.

,$er%me&t &%t%al [] /mol

dm3

&%t%al [O0] /

mol dm3

&%t%al rate o+

rea-t%o& /moldm

3m%&

1

2., - ,2

2., - ,2

4., - ,9

2 2., - ,2

4., - ,2

4., - ,9

9 4., - ,2

4., - ,2

?., - ,9

"i$ Ded'ce the rate e%pression for the reaction.

(3)

"ii$ Determine the val'e of the rate constant for the reaction andstate its 'nits.

(2)

"iii$ 6tate the name of isomer and e%plain yo'r choice.(2)


16/26

"iv$ 6tate e&'ations for the steps that take place in the mechanism ofthis reaction and state which of the steps is slow and which is fast.

(2)(Total 11 marks)

17. his &'estion refers to the following reaction.

2( 2 ) 2

he reaction occ'rs in a series of steps.

2) 2 slow ( ) fast

*hat is the rate3determining step for this reaction mechanism+

/. 2( 2 ) 2

!. 2( ) (

C. 2) 2

D. ( ) (Total 1 mark)


17/26

1. his &'estion refers to the following reaction.

2( 2 ) 2

he reaction occ'rs in a series of steps.

2) 2 slow ( ) fast

*hat is the rate e%pression for this reaction+

/. rate 0 k1

!. rate 0 k1212

C. rate 0 k12

D. rate 0 k12(Total 1 mark)

1!. Consider the following reaction.

;!r"a&$ ( !rO9

"a&$ ( @

("a&$ ) 9!r2"a&$ ( 9@2O"l$

he rate e%pression for the reaction is fo'nd to 8eA

rate 0 k1!r 1!rO9

1@

(2

*hich statement is correct+

/. he overall order is 2.

!. Do'8ling the concentration of all of the reactants at the same timewo'ld increase the rate of the reaction 8y a factor of .

C. he 'nits of the rate constant7 k7 are mol dm9

s

.

D. / change in concentration of !ror !rO9

does not aFect the rate of the

reaction.(Total 1 mark)


18/26

2". he rate e%pression for a reaction isA

rate 0 k 11

*hich statement is correct+

/. /s the temperat're increases the rate constant decreases.

!. he rate constant increases with increased temperat're 8't event'allyreaches a constant val'e.

C. /s the temperat're increases the rate constant increases.

D. he rate constant is not aFected 8y a change in temperat're.(Total 1 mark)

21. Consider the following reaction mechanism.

6tep @2O2( #) @2O ( #O

slow

6tep 2 @2O2( #O) @2O ( O2( #

fast

*hich statement correctly identies the rate3determining step and thee%planation+

/. 6tep 2 8eca'se it is the faster step

!. 6tep 8eca'se it is the slower step

C. 6tep 8eca'se it is the rst step

D. 6tep 2 8eca'se it is the last step(Total 1 mark)


19/26

22. Nitrogen mono%ide reacts at 2?,


20/26

"ii$ #dentify the intermediate involved in the reaction.(1)

(Total 2 marks)

24. he conversion of C@9NC into C@9CN is an e%othermic reaction which can 8e

represented as follows.

C@9NPC transition state C@9CPN

his reaction was carried o't at diFerent temperat'res and a val'e of therate constant7 k, was o8tained for each temperat're. / graph of ln k againstQT is shown 8elow.

"i$ Dene the term activation energy7 Ea.

(1)

"ii$ Constr'ct the enthalpy level diagram and la8el the activation energy7Ea7 the enthalpy change7 IH7 and the position of the transition state.

(3)

"iii$ Descri8e &'alitatively the relationship 8etween the rate constant7 k7and the temperat're7 T.

(1)


21/26

"iv$ Calc'late the activation energy7 Ea7 for the reaction7 'sing a8le of

the Data !ooklet.(4)

(Total ! marks)

25. wo species7 and L7 react together according to the following e&'ation.

( L ) M

he accepted mechanism for this reaction is

( 2 fast 2( L ) M (

slow

*hat is the order with respect to and L+

9 :

/.

!. 2

C. 2

D. 2 2

(Total 1 mark)

26. he activation energy of a reaction may 8e determined 8y st'dying theeFect of a partic'lar varia8le on the reaction rate. *hich varia8le m'st 8echanged+

/. p@

!. Concentration

C. 6'rface area

D. emperat're(Total 1 mark)


22/26


23/26

3". *hat is the order of reaction with respect to NO2"g$ and >2"g$ given the

following rate data at a certain temperat're+

[NO2(8)] / mol dm3

[F2(8)] / mol dm3

Rate / mol dm3

m%&1

,. ,.2 ,.

,.2 ,.2 ,.4

,. ,.4 ,.2

Order ;%t< res$e-tto NO2(8)

Order ;%t< res$e-tto F2(8)

/. rst rst

!. rst second

C. second rst

D. second second

(Total 1 mark)

31. Nitrogen"##$ o%ide reacts with hydrogen according to the following e&'ationA

2NO"g$ ( 2@2"g$ ) N2"g$ ( 2@2O"g$

he ta8le shows how the rate of reaction varies as the concentrations of thereactants are changed.

,$er%me&t&%t%al [NO] /

mol dm3

&%t%al [02] /mol

dm3

&%t%al rate /mol

(N2) dm3

s1

,.,, ,.,, 2.;9-,

2 ,.,, ,.2,, ;.,;-,

9 ,.2,, ,.,, .,-,;

4 ,.9,, ,.,, 2.2?-,;


24/26

"a$ Determine the order of reaction with respect to @2and with respect to

NO.

@2 ............................................................................................................

....................

NO ..............................................................................................................................

(2)

"8$ *rite the rate e%pression for the reaction.

.....................................................................................................................................

(1)

"c$ Calc'late the val'e for the rate constant7 and state its 'nits 'sing thedata from e%periment .

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(2)


25/26

"d$ / s'ggested mechanism for this reaction is as follows.

@2( NO fast step ( NO ) ( @2O slow step ( @2) N2( @2O

fast step

6tate and e%plain whether this mechanism agrees with thee%perimental rate e%pression in "8$.

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(4)

"e$ B%plain why a single step mechanism is 'nlikely for a reaction of thiskind.

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(2)

"f$ Ded'ce and e%plain how the initial rate of formation of @2O compares

with that of N2.


26/26

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(2)(Total 13 marks)

chem kinetics ib questions

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