chem kinetics ib questions
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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)
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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)
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"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 :;,
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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)
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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)
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!. 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&$2
*hich graph is consistent with this information+
(Total 1 mark)
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1". /le% and @annah were asked to investigate the kinetics involved in theiodination of propanone.hey were given the following e&'ation 8y theirteacher.
C@9COC@9"a&$ ( #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.
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(1)
"8$ "i$ Ded'ce the order of reaction for each s'8stance and the rate
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e%pression from the res'lts.
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(2)
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"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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(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
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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)
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"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 ;,,
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13. Consider the following reaction.
NO2"g$ ( CO"g$ ) NO"g$ ( CO2"g$
/t T K 22:
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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)
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"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)
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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)
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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)
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22. Nitrogen mono%ide reacts at 2?,
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"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)
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"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)
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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.
,$er%me&t&%t%al [NO] /
mol dm3
&%t%al [02] /mol
dm3
&%t%al rate /mol
(N2) dm3
s1
,.,, ,.,, 2.;9-,
2 ,.,, ,.2,, ;.,;-,
9 ,.2,, ,.,, .,-,;
4 ,.9,, ,.,, 2.2?-,;
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"a$ Determine the order of reaction with respect to @2and with respect to
NO.
@2 ............................................................................................................
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NO ..............................................................................................................................
(2)
"8$ *rite the rate e%pression for the reaction.
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(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)
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"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.
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(2)(Total 13 marks)