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Form 5 Chapter 3
CHAPTER 4 : THERMOCHEMISTRY ANALYSIS ANALYSIS OF PAST PAST YEAR QUESTIONS QUESTIONS FROM 2003 – 2008 2008 Year Paper No. Type of question Question No
2003
2004
2005
P2
P3
P2
P3
P2
P3
S E
S E
S E
S E
S E
S E
6
4
3 5
2007
2006
2008
P3
P2
P3
P2
P3
S E
S E
S E
S E
S E
1
6
P2
S E
1
1. SPM 2003/P2/Q6 A student student carried out out an experiment to determine determine the heat heat of displacement displacement for the reaction between copper and silver nitrate solution. In this experiment, excess copper powder was added 3
-3
to 100 cm of silver nitrate solution 0.5 mol dm . The heat of displacement in this experiment -1
was -105 ! mol . -1
-1
-3
"#pecific heat capacit$ of the solution is %.& !' ( , and the densit$ of the solution is 1 ' cm )
(1) *hat is meant b$ heat of displacement displacement + "1 mark )
(2) esides the data 'iven above, state one other piece of data that is needed to calculate the heat of displacement. displacement. "1 mark ) one precaution that must be taen while carr$in' out the experiment. (3) #tate one precaution "1 mark ) d/ i i/ #tate one observation one observation of the experiment.
(2)
. . "1 mark ) #tate the reason for the observation in d/ i/ . . "1 mark
)
1
1
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Form 5 Chapter 3
(5) ased on the information from this experiment, calculate (9)
the number of moles of silver ions reacted.
"1 mark )
(2)
the amount of heat released.
"1 mark )
(3)
the chan'e in temperature.
"1 mark )
(6) raw an ener'$ level dia'ram for the t he reaction in this experiment.
"& marks )
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Form 5 Chapter 3
(7) The experiment is repeated usin' 100 cm 3 of 1.0 mol dm-3 silver nitrate solution and excess copper powder. (alculate the temperature chan'e in this experiment. xplain wh$ this chan'e of temperature is different from that in e/ iii/. "3 marks)
2. SPM 2004/P2/Q4 2i'ure %3show the set-up of the apparatus of an experiment to determine the heat of- precipitation. -3 3 &5.0 cm of 0.5 mol dm silver nitrate solution is reacted with &5 cm of 0.5 mol dm 3
sodium chloride solution. As a result there is a chan'e in temperature of the mixture and a white precipitate is formed.
efore reaction
After reaction
Figure 4
3
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Form 5 Chapter 3
(2) *h$ is a pol$st$rene cup used in the experiment + "1 mark )
(1)
(2)
ased on the chan'e of temperature in the experiment, state the t $pe of reaction that occurred. . "1 mark ) ow is the total ener'$ of the product different from the total ener'$ of the reactants+ . "1 mark )
(3) #tate one step that should be taen while addin' the two solutions in order to 'et a more accurate result. "1 mark ) (4) The ionic e4uation for the precipitation reaction of silver chloride is 6 a4/ 6
A'
(9)
-
(l a4/
A'(ls/ 6
-
*hat is the number of moles of A' ions that reacted with (l ions +
"1 mark )
(2)
(alculate the heat chan'e of the precipitation reaction that has taen place. 7se the -1 -1 information that the specific heat capacit$ of water is %.& ! ' °( and densit$ water -3 is 1 ' cm .
"& marks)
4
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iii/
Form 5 Chapter 3
(alculate the heat of precipitation for this reaction.
"& marks) (5) The calculated value of the heat of precipitation for this reaction is less than the actual value. 8ive a reason. "1 mark )
3. SPM 2005/P2/Q3 A pupil carried out an experiment to determine the value of heat of displacement. 2i'ure 3 shows the set up of the apparatus used in the experiment.
9inc :owder
8lass cup (opper II/ sulphate #olution
Figure 3 The followin' data was obtained o
Initial temperature of copperII/ sulphate solution, θ1 ; &< ( i'hest temperature of the mixture of product, θ&
o
; %< (
(1) (omplete the ionic e4uation for the reaction that occurred.
9n 6 (u
&6
. "1 mark )
5
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Form 5 Chapter 3
(2) In this experiment, excess =inc is added to 100 cm 3 of 0.5 mol dm-3 copperII/ sulphate solution. -1 o -1 8iven that the specific heat capacit$ of the solution is %.& ! ' ( and the densit$ of -3 the solution is 1.0 ' cm . (1)
(alculate the chan'e of heat capacit$ of the experiment. 7se the formula, ∆ ; mcθ
"& marks)
(2)
(alculate the heat of displacement in the experiment. The number of moles of copperII/ sulphate that reacted ; ...... eat of displacement
; ...
"& marks)
(3) raw the ener'$ level dia'ram for the reaction.
"& marks)
(4) It was found that the heat of displacement value in b/ii/ is not the same as the actual value. #u''est one step that must be taen to 'et a more accurate value. "1 mark )
(5) ased on the experiment, what is meant b$ the heat of !s"#a$eme%t + "1 mark )
(6) The pupil repeats the experiment, replacin' the metal =inc with metal >. The followin' e4uation shows the reaction and the value of heat of displacement of metal iron and metal >.
6
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Form 5 Chapter 3
4uation I 2e s/ 6 (u#? % a4/
2e#?% a4/ 6 (us/, ∆ ; -150 ! mol
-1
4uation II >s/ 6 (u#?% a4/
>#?% a4/ 6 (us/,
∆
; - 100 ! mol
-1
:redict the metal >. (hoose from this list Aluminium, ma'nesium and tin. "1 mark )
4. SPM 2005/P2/Q5 (1) *hat is the meanin' of the heat of $om&'st!o% of a% a#$oho# + "1 mark )
(2) Table 5 shows the heat of combustion of three t$pes of alcohol. The number of carbon atoms and the attractive force between molecules are amon' the factors that affect the value of heat of combustion. Name of alcohol
Molecular formula
@ethanol thanol :ropanol
(3? (&5? (3?
Hea of com!u"ion #$% &' mol &5 13B &015
Ta!le (
(1)
7se data from Table 5 to draw the 'raph of the heat of combustion a'ainst number of carbon atoms on the 'raph paper provided. "& marks)
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(2)
Form 5 Chapter 3
ased on the 'raph in b/i/, as t he number of carbon atoms increases so does the value of the heat of combustion. xplain wh$. "& marks)
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(3)
Form 5 Chapter 3
(alculate the heat released when &.3' of ethanol is completel$ burnt in air. 8iven that the relative atomic mass of (;1&, ;1, ?;1B. 7se the formula eat released ; Cumber of moles > eat of combustion.
"& marks)
(3) @ethanol and ethanol do not have isomers. :ropanol has two isomers. raw the structures of the two isomers of propanol.
"& marks)
(4) Table 5.& shows the free=in' and the boilin' points of mercur$, methanol, ethanol and butanol. +
Free)ing *oin # C -3D -D -11A -D0
Su!"ance @ercur$ @ethanol thanol utanol
+
,oiling *oin # C 35A B% AD 11A
Ta!le (-. A thermometer ma$ contain mercur$ or an alcohol. 0 A mercur$ thermometer is not suitable to measure the temperature at around -100 (. Came a suitable alcohol that can be used in a thermometer to measure the temperature at 0 around E100 (. 8ive one reason for $our choice. Came of alcohol .... Feason .... .... .... "& marks)
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5. SPM 2006/P3/Q1 ia'ram 1.1 shows two experiments to determine the heat of neutralisation. E/*erimen I 3
-3
Feaction between &5 cm of sodium h$droxide solution, Ca?, &.0 mol dm and &5 cm -3 of ethanoic acid, ( 3(??, &.0 mol dm .
Initial temperature of mixture
G(
i'hest temperature of mixture G( (han'e in temperature
G(
E/*erimen II 3
-3
Feaction between &5 cm of sodium h$droxide solution, Ca?, &.0 mol dm and &5 cm -3 of h$drochloric acid, (l, &.0 mol dm .
Initial temperature of mixture
T1 G(
i'hest temperature of mixture
T& G(
(han'e in temperature
T3 G( 0iagram '-'
3
3
10
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Form 5 Chapter 3
(1) *rite the initial and the hi'hest temperature of the mixture and chan'e in temperature for xperiment I in ia'ram 1.1. "3 marks)
b/
(onstruct a table that can be used to record the data from both experiments.
"3 marks)
(3) #tate one h$pothesis for both experiments. "3 marks)
(4) ased on the temperature in xperiment I, predict the predict the chan'e in temperature in xperiment II. "3 marks)
(5) *h$ must the initial temperature and the hi'hest temperature be recorded in these experiments+ "3 marks)
(6) ow can the value of the chan'es in temperature be obtained+ "3 marks)
(7) #tate hree observations that $ou could obtain in xperiment I other than the chan'e in temperature. 1 &
11
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Form 5 Chapter 3
3 "3 marks) (8) #tate hree constant variables in this experiment. 1 & 3 "3 marks)
(1) ia'ram 1.& shows the calculation to determine the heat of neutrali=ation for the reaction in xperiment I and xperiment II. E/*erimen I
E/*erimen II
eat release ; mcθ
eat release ; mcθ
; 50 ' x %.& %.& ! '-1 o(-1 x o(
; 50 ' x %.& %.& ! '-1 o(-1 x T3 o(
; ( !
; ) !
eat of neutrali=ation
eat of neutrali=ation
;
;
( ! HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH Cumber of mole of water produced
$ ! HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH Cumber of mole of water produced
0iagram '-. ased on ia'ram 1.& (1) 8ive the operational definition for the heat of neutrali=ation. . . "3 marks)
(2)
It was found that the value of ) is 'reater than the value of ( . xplain wh$. . . "3 marks)
(10) The experiment is repeated usin' the methanoic acid. The values of the heat of neutrali=ation of these acids are 'iven in Table 1. (omplete Table 1 b$ classif$in' the acids as stron' acid or wea acid.
12
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Name of aci1 thanoic acid
Form 5 Chapter 3
Hea of neurali)aion#$% mol -50.3
$drochloric acid
-5A.&
@athanoic acid
-50.5
&'
T2*e of aci1
Ta!le '
"3 marks)
6. SPM 2007/P3/Q1 ia'ram 1.1 shows the apparatus set-up for experiments I, II, III and I. The ma'nification of the thermometers shows the readin's of the initial temperature and the hi'hest or lowest temperatures in each experiment.
(1) i/ Fecord the temperature readin's in the spaces provided in ia'ram 1.1. "3 marks)
Exper i mentI
Ex pe r i me ntI I
Ex pe r i me ntI I I
13
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Form 5 Chapter 3
Ex pe r i me ntI V
0iagram '-'
(2)
(onstruct a table to show all the data in each of these experiments.
"3 marks)
(3)
(lassif$ the reactions in these experiments as either exothermic reactions or endothermic reactions. E/ohermic reacion
En1ohermic reacion
"3 marks)
(2) A student repeated xperiment I several times. (1) #tate hree thin's must be ept constant in these experiments. 1 & 3 "3 marks)
14
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(2)
Form 5 Chapter 3
#tate the h$pothesis for xperiment I. . . "3 marks)
(3) ased on xperiment II (1) #ate the temperature chan'e and 'ive o reasons for the chan'e. Temperature chan'e . Feason1 . Feason& . "3 marks)
(2)
#ate the operational definition for the reaction that taes place. . . "3 marks)
(4) The reaction in xperiment III is a neutrali=ation reaction. ?ther acids can be substituted for h$drochloric acid.
These acids have the same volume and concentration as the h$drochloric acid in xperiment III. :redict the temperature in the neutrali=ation reactions of these acids. o
1. #ulphuric acid .. ( &. Citric acid .. o( o
3. thanoic acid .. ( "3 marks)
15
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e/
Form 5 Chapter 3
ia'ram 1.& shows some observations in experiment I.
0iagram '-.
(1)
#tate hree observations shown in ia'ram 1.&. 1 & 3 "3 marks)
(2)
The followin' chemical e4uation represents the reaction in xperiment I. (la4/ 6 Ca(? 3a4/ J Ca(la4/ 6 (?&'/ 6 &?l/ ased on the chemical e4uation, and the answer in 1e/i/, what inference can be made from xperiment I+ . . "3 marks)
(3)
#etch a 'raph to show the chan'e in the volume of carbon dioxide 'as produced a'ainst time.
"3 marks)
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.
Form 5 Chapter 3
SPM 2008/P2/Q6
The thermochemical e4uation for the neutrali=ation reaction between nitric acid and sodium h$droxide solution is 'iven below. C?3 6 Ca?
CaC?3 6 &? , K ; -5.3 ! mol
-1
(1) #tate the meanin' of heat of neutralisation. "1 mark ) (2) ased on the 'iven thermochemical e4uation, state one observation when dilute nitric acid is added to sodium h$droxide solution. xplain $our answer. "& marks) 3 -3 3 (3) In an experiment, 100 cm of & mol dm nitric acid solution was added to 100 cm of & -3 mol dm sodium h$droxide solution. -1 o "#pecific heat capacit$ of solution ; %.& ! ' ( 1 -3 L ensit$ of solution ; 1 ' cm ) (alculate (9) The heat ener'$ released in this experiment,
"& marks)
(2)
The temperature chan'e in this experiment.
"& marks) d/ raw the ener'$ level dia'ram for the reaction between nitric acid and sodium h$droxide.
"& marks)
17
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Form 5 Chapter 3
(5) Citric acid and ethanoic acid both react with sodium h$droxide b$ a neutralisation reaction. C?3 6 Ca? 6 Ca?
-1
CaC?3 6 &? , K ; -5.3 ! mol (3(??
(3(??Ca 6 &? , K ; -55.& ! mol
-1
xplain wh$ the heat of neutralisation for each reaction is sli'htl$ different. .. "& marks)
18
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CHAPTER 4 : THERMOCHEMISTRY
1. SPM 2003/P2/Q6 (1) eat change when 1 mol of metal is displaced from its salt solution b$ a more electropositive metal. (2) Initial temperature and hi'hest temperature. (3)
1. #tir the mixture. 2. Add the two solutions as 4uicl$ as possible. 3. 7se pol$st$rene or plastic cup an$ one/
(4) i/ 1. 8re$ solid is deposited 2. (olourless solution turns blue 3. The thermometer readin' rises or the container becomes hot or warm. an$ one/
(2)
e/ i/
1. #ilver metal is produced 2. copperII/ ion is produced 3. exothermic reactionM heat is released to the surroundin's ; 0.5 x 100; 0.05 mol 1000
ii/
; 0.05 x 105 ! ; 5&50 !
iii/
N ; 5.&5 x 1000 ; 1&.5 ( 100 x %.&
o
f/ ner'$ (u 6 A'6 -1
K ; -105 ! mol &6
(u
(7)
6
1. @ol of A'
; 1 x 100 ; 0.1 mol 1000
6 A'
1
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Form 5 Chapter 3
o
&. eat chan'e, N ; 0.1 x 10500 ; &5 ( 100 x %.&
3. Cumber of mol of A'6 is double or concentration of silver nitrate is double. 2. SPM 2004/P2/Q4 (1) To re1uce the heat loss to the surroundin's. (2) i/ xothermic reaction (2)
Total ener'$ of products is le"" than total ener'$ of reactants
(3) @ix the solutions uic$l2 and "ir the reaction mixture. (4) i/ Cumber of moles A'6 ; &5 x 0.5 100 1=0.01&5 mol (2) The heat chan'e ; mcO 1= 50 x %.& x 31.5-&D.0/ 2= 5&5 ! (3)
6
-
0.01&5 mol of A' ions that reacted with (l ions released 5&5 ! 6
-
1 mol of A' ions that reacted with (l ions released ;
525 0.0125
!
; %&000 ! -1
eat of precipitation ; -%& !mol e/ eat is relea"e1 to surroundin's. 3. SPM 2005/P2/Q3 a/
9n&6 6 (u
b/
i/
K ; 100 x %.& x
ii/
Cumber of moles (u#?% reacted ; 0.5 x 1 00
&0 ; <%00 %
eat of displacement
; 0.05 mol 1000 ; HHH mcOHHHHHHH Cumber of moles ; <%00 0.05 -1 ; -1B< 000 ! mol -1 ; -1B< ! mol
20
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c/
ner'$ &6
9n
6 (u K ; -1B< ! mol &6
9n
(4)
-1
6 (u
1. 7se a *la"ic M *ol2"2rene cup 2. add the =inc powder uic$l2. 3. "ir the solution an$ one/
(5) The heat released when ' mole of co**er is displaced from its solution. (6) Tin #n/ 4. SPM 2005/P2/Q5 (1) The heat released when 1 mole of alcohol is com*leel2 !urn in excess ox$'en. b/ i/
1.
2.
all *oin" are transferred correctl$
draw a "raigh line
(2)
The 'reater the number of carbon dioxide molecules, more products are formed which causes more heat to be released durin' the formation of bonds.
(3)
Felative molecular mass of ethanol 1=1& x &/ 6 1 x B/ 6 1B ; %B Cumber of moles ethanol ; &.3 ; 0.05 mol %B eat released ; 0.05 x 13B B<.< ! 1= 2= B< <00 !
c/
(4) - thanol o o - The free=in' point of ethanol is -11 (, which is lower than -100 (. 5. SPM 2006/P3/Q1 a/ I nitial temperature of mixture
o
&<.0 (
i'hest temperature of mixture
o
%0.0 (
21
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Form 5 Chapter 3
(han'e in temperature
o
1&.0 (
b/ E/*erimen Initial temperature of o mixtureM ( i'hest l temperature of o mixtureM ( o (han'e in temperatureM (
E/*erimen I &<.0
E/*erimen II T1
%0.0
T&
1&.0
T3
(3) #tron' acid produces hi'her heat of neutrali=ation than wea acid. (4) 1&.5 o( - 15.0 o( (5) To enable us to obtain the chan'e in temperature for both experiments. (6) (han'e in temperature ; i'hest temperature of mixture - Initial temperature of mixture (7) 1. A colourless mixture of solution is obtained. 2. The vine'ar smell of ethanoic acid disappears. 3. The pol$sterene cup becomes hot. 4. Thermometer readin' is rises (8) 1. The volumes of the acid and the alali. 2. The concentrations of the acid and the alali. 3. The t$pe of cup used in the experiment. (9) i/ The heat of neutrali=ation is defined as the amount of heat released when 1 mole of water is produced. (2)
xperiment II uses a stron' acid whereas xperiment I uses a wea acid.
P/ Name of aci1 thanoic acid $drochloric acid @ethanoic acid
T2*e of aci1 *ea acid #tron' acid *ea acid
B. SPM 2007/P3/Q1 a/ i/
E/*erimen I E/*erimen II E/*erimen III E/*erimen I
Iniial em*eraure o 5 C6 &<.0 &D.0 &A.0 30.0
Highe" o em*eraure 5 C6 3B.0 &5.0 3&.0 &.0
Iniial em*eraure o 5 C6
Highe" o em*eraure 5 C6
ii/ E/*erimen
22
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Form 5 Chapter 3
I II III I
&<.0 &D.0 &.0 30.0
E/ohermic reacion xperiment I xperiment III
iii/
3B.0 &5.0 3&.0 &.0
En1ohermic reacion xperiment II xperiment I
(2) i/ 1. The mass of sodium h$droxide. 2. the volume of water in the cup. 3. The si=e of the pol$st$rene cup. (2)
The reaction between sodium h$droxide and water is an exothermic reaction.
(3) i/ Temperature chan'e ; % o( Feason 1 eat ener'$ is absorbed b$ the reactants from the surroundin's. Feason & The ener'$ of the products is more than the ener'$ of the reactants.
(35) The decrease in temperature shows that endothermic reaction happens where heat ener'$ is absorbed from the surroundin's. (4) 1. 3 o( o &. 3& ( o 3. 30 ( (5) i/ 1. 2inal temperature is lower than the initial temperature. 2. The temperature readin' decreases. 3. ubbles of 'as are released. (35) eat ener'$ is absorbed when h$drochloric acid reacts with sodium h$dro'en carbonate to produce sodium chloride, carbon dioxide and water. iii/ !o"u#e of $ar%on 3 &io'i&e (as)*$#
Ti#e *#inute
23
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7. SPM 2008/P2/Q6 (1) Hea change when ' mole of h21rogen ion" reacts with ' mole of h21ro/i1e ion" to form 1 mole of water. (2) ?bservation the mixture becomes hot or temperature increase xplanation the reaction is e/ohermic
(3) i/ Co. of moles of Ca? ; 100 x & ; 0.& mol 1000 ner'$ released ; 0.& x 5.3 1= 11.%B !
(2) d/
Temperature chan'e ; 11.%B x 1000 &00 x %.& o ; 13.B (
ner'$
Ca? 6 C?3 K ; -5.3 ! mol-1
Ca C?3 6 &?
(5)
1. thanoic acid is a wea acid which partiall$ ioni=e in water, nitric acid is stron' acid that ioni=e completel$ in water. 2. ener'$ is used to ioni=eMdissociate wea acid.
