(13)thermochemistry

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CHAPTER 12: THERMOCHEMISTRY

MULTIPLE CHOICE QUESTIONS

INSTRUCTION : Answer allquestions.

1. Which of the following is an endothemic reaction?

A Precipitation of silver chlorideB Displacement of iron by magnesiumC Decomposition of magnesium sulphate hydrateD Dilution of sulphuric acid with water

2. Which of the following is not trueabout eothermic reaction?

A !he bond is formed

B !he temperature of the miture increasesC !he heat is absorbed from the surroundingD !he energy content of the reactants is higher than the energy content of the products

". Which of the following reactions occurs when ice change to water ?

A #ndothermicB #othermicC DecompositionD $eutrali%ation

&. 'ne mole of hydrogen ion reacts with one mole of hydroide ion to form one mole ofwater.

!he above statement refers to

A heat of displacementB heat of neutrali%ationC heat of combustionD heat of precipitation

(. !he reaction between magnesium ribbon and iron)**+ sulphate solution can be used todetermine the heat of

A displacementB neutrali%ationC combustionD precipitation

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,. !he diagram shows the energy level diagram of a reaction

#nergy Products

-eat of reaction

eactants

Which of the following reactions represents the above energy level diagram?

A eothermic reactionB endothermic reactionC neutrali%ation reactionD combustion reaction

/. Which of the following informations is not neededto deteermine the heat of precipitation?

A !he 0uantity of reactantsB !he number of moles of reactantsC !he changes of temperature of the mied reactionD !he time ta1en for the precipitate to occur

8. Why is a copper can used in the eperiment to determine the heat of combustion ?

A As heat insulatorB Conduct heat easilyC educe the heat loss

D -ave higher melting point

3. Which of the following is an eothermic reaction ?

A Dissolving ammonium chloride in waterB -eating copper)**+ sulphate hidrateC $eutrali%ing hydrochloric acid with sodium hydroide solutionD 4iing hydrochloric acid with potassium hydrogen carbonate

56. What happen when the eothermic reaction occurs?

* -eat is released** !he surrounding temperature increases*** !he energy released is more than the energy absorbed*7 8tronger bond is formed and wea1er bond is bro1en

A * and ** onlyB *** and *7 onlyC * ** and *** onlyD * ** *** and *7

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55. Why is the bea1er feels cold when ammonium chloride is added into a bea1er thatcontains water ?

A -eat is absorbed from the waterB A strong bond is formedC 8pecific heat of water is decreased

D 9oss of heat to the surrounding

52. A polystyrene cup is used in the eperiment to determine the heat of reaction because

* it is very light** it does not absorb heat from the solution*** it does not conduct heat to the surrounding*7 it ensures that the reaction reacts completely

A * and ** only

B ** and *** onlyC * ** and *** onlyD * ** *** and *7

5". What is the information needed to determine the heat of neutrali%ation between acid andal1ali ?

* *ncreased in the temperature of reaction miture** 7olume of acid and al1ali used*** Concentration of both solutions used

*7 8pecific heat of solution for miture reaction

A * and ** onlyB *** and *7 onlyC * ** and *7 onlyD * ** *** and *7

5&. Which of the following is not an endothermic reaction?

A 4elting of naphthaleneB PhotosynthesisC #vaporation of waterD usting of iron

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5(. !he diagram shows the set up of the apparatus of an eperiment to determine the heat ofneutrali%ation between an acid and an al1ali

thermometer

polystyrene cup

miture of acid and al1ali

Why is polystyrene cup used?

A 9ight and cheapB Act as heat insulatorC 4ore safely than glass containerD $ot easily corrode by acid and al1ali

5,. What is the meaning of heat of combustion ?

A Combustion for 5 mole of fuelB Combustion of 5 mole of fuel with oygenC Complete combustion of 5 mole of fuel with 5 mole of oygenD Complete combustion of 5 mole of fuel with ecess oygen

5/. Which of the following statements is true about eothermic reaction?

* Brea1ing of bond occurs** Dissolving ammonium chloride in water*** Chemical reaction that released energy to the surrounding*7 $eutrali%ation between hydrochloric acid with potassium hydroide solution

A * and ** onlyB *** and *7 onlyC ** *** and *7 onlyD * ** *** and *7

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5:. Which of the following energy level diagram is ehotermic reaction?

A energy B energyreactants reactants

H neg!ti"e H#ositi"e

#ro$u%ts #ro$u%ts

C energy & energy

#ro$u%ts #ro$u%ts

H neg!ti"e H #ositi"e

reactants reactants

1'. !he temperature of a miture decreases when

A a piece of potassium is added into waterB ammonium nitrate is dissolved in waterC %inc powder is added into copper )**+ sulphate solutionD dilute sulphuric acid is added into sodium hydroide solution

26. !he following e0uations show neutrali%ation reactions

-Cl )a0+ ; $a'- )a0+ $aCl)a0+; -2')l+< = - > (/." 1

C-"C''- )a0+ ; $a'- )a0+ C-"C''$a )a0+; -2')l+< = -> @((. 1

!he heat of reaction =- for the above reactions are different because ethanoic acid

A can easily conduct heatB will loose heat energy to the surroundingC absorb parts of the heat energy for ioni%ationD has one hydrogen ion that is replace with sodium ion

25. -eat of combustion for different type of alcohols are shown below

Alcohol 4ethanol #thanol Propanol Butanol

=- 1 mol5 5"/6 262( 2,:6

Which of the following is the suitable value of ?

A 565( 1 mol5 B /5( 1 mol5

C 35( 1 mol5 D ,5( 1 mol5

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22. !he following e0uation shows the reaction of the formation of ammonia.

$2; "-2 2$-"

#othermic reaction occurs becauseA the heat released is more than the heat absorbed

B the value of heat change is positiveC total energy of the product is more than total energy of the reactantD higher temperature will increase the 0uantity of the product

2". Which e0uation below is endhotermic reaction?

A -2')g+ -2')l+B C'2)g+ C'2)s+C CuC'")s+ Cu')s+ ; C'2)g+D $a'-)a0+; -Cl)a0+ $aCl)a0+; -2')l+

2&. Why is the reaction between wea1 acid and strong al1ali released less than (/ 1 mol5 of

heat energy?

A strong al1ali ioni%e completelyB wea1 acid always absorb heatC strong al1ali has strong bondD heat is used to ioni%e wea1 acid

2(. !he e0uation below shows the reaction between hydrochloric acid and sodium hydroidesolution.

-Cl )a0+; $a'-)a0+ $aCl)a0+; -2')l+ = - > (/ 1 mol5

Which of the following e0uation have the same heat of reaction with the above e0uation?

A -$'")a0+; $-&'- )a0+ $-&$'")a0+ ; -2')l+B -$'")a0+; '-)a0+ $'")a0+; -2')l+C C-"C''-)a0+ ; $-&'- )a0+ C-"C''$-&)a0+; -2'D C-"C''-)a0+ ; '-)a0+ C-"C'')a0+; -2')l+

2,. Why is the heat of combustion for propanol is higher than the heat of combustion ofmethanol ?

A !he molecular mass of propanol is higher than molecular mass of methanolB Propanol is more reactive than methanolC Propanol is easily burn than methanolD Propanol has 5 carbon atom and 2 hydrogen atom more than methanol

2/. -eat of combustion for different type of al1ane is shown below

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4aterial-eat of combustion

= - 1 mol5

4ethane C-& ::2.6

#thane C2-, 5(&2.&

Butane C&-56 2://."

What is the value of heat of combustion for propane C"-:

A :6( 1mol5

B 3&2 1mol5

C 2262 1mol5

D 23&& 1mol5

2:. !he following is an e0uation for a reaction

Cu8'&; 2$a'- E Cu)'-+2; $a28'& =- >p 1 mol

5

Which of the following represents =- in the above e0uation?

A heat of displacementB heat of neutrali%ationC heat of combustionD heat of precipitation

23. !he reaction between %inc and copper )**+ sulphate solution is an eothermic reaction.Which of the following energy level diagrams represent the reaction?

A energy C energyCu2;; Fn Cu ; Fn2;

Cu ; Fn2; Cu2; ; Fn

B energy & energy

*n + Cu2+

*n + Cu2+

*n + Cu2+ *n2++ Cu

"6. When ecess magnesium is added to &66 cm"of ( mol dm"of copper )**+ sulphate

the temperature increase from "66C to "26C. What is the heat of displacement of copper ?

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2,/(

265/

5"/,

/5(

He!t o- %o/ustion0

o1

Nu/er o- %!r/on !tos #er !%oo

oe%ue

1 2 3 4 (

G spesific heat capacity > &.2 g5 6C5H

A 5,:6 mol@5 C ,/26 mol5

B "",6 mol5 D 5,:66 mol5

"5. An eperiment is carried out by miing ecess magnesium with (6 cm"of 6.2( mol dm"

of iron )**+ chloride. !he energy level diagram for the reaction is shown below.

4g)s+; IeCl2)a0+ #nergy

5- > 265., 1 mol5

4gCl2)a0+; Ie)s+

What is the temperature change in the eperiment?

G 8pecific heat capacity > &.2 g

5 6

C

5

H

A 5.66C C 3., 6CB 5.2 6C D 52.6 6C

"2. !he graph shows the heat of combustion of alcohol against the number of carbonatom per alcohol molecule.

Calculate theheat released when , g ofpropanol is burnt ?

Gelative atomic mass C52< -5< '5,H

A 5/3.( 1

C 26:./ 1B 265./ 1 D 25,.3 1

"". When 5.: g of glucose is burnt in a bom calorimeter the heat released increase thetemperature of (66cm"of water by 5"6C. Calculate the heat of combustion of glucose.G elative molecular mass of glucose>5:6< specific heat capacity of

water> &.2 g5 6C5H

A 2/"6 1 mol5

B 2/"66 1 mol5

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C 2/"6 1 mol5

D 2/:66 mol5

"&. !he combustion of 6."2 g of methane increase the temperature of 2(6 cm"water from2:6C to &,6C. Calculate the heat of combustion of methane.

G C52< -5< specific heat capacity> &.2 g6C5H

A @ &26 1 mol5

B @ ,/& 1 mol5

C @ 3&( 1 mol5

D @ 56(, 1 mol5

"(. When 6./2g of pentene is completely burnt the heat released caused 266 cm"of waterchange from 2(6C to ,66C. Calculate the heat of combustion of pentane ?

A 23&6 1 mol5

B ""(6 1 mol5

C "/:6 1 mol5

D &2:6 1 mol5

",. When 2( cm"of 2.6 mol dm"sodium hydroide solution is mied with 2( cm"of

2.6 mol dm"nitric acid the temperature rise by 5&6C. Calculate the heat change.

G 8pecific heat capacity> &.2 g6C5 H

A 5&/6 B 2"(2 C 23&6 D "2:6

"/. !he combustion of 5.:g of glucose released heat that increase the temperature of (6cm"of water by ,.(6C. Calculate the heat of combustion of glucose.

G elative atomic mass C52< -5< specific heat capacity> &.2 g6C5H

A /(.: 1 mol5

B 3".& 1 mol5

C 5",.( 1 mol5

D 25,." 1 mol5

":. !he following e0uation shows a reaction.

-Cl)a1+; $a'-)a1+ $aCl)a1+; -2')ce+ - >(& 1 mol@5

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Calculate the increase in temperature of a solution when ,6 cm"of 6.( mol dm"of

hydrochloric acid reacts with (6 cm"of 6.( mol dm"of sodium hydroide solution.

G8pecific heat capacity> &.2 g6C5H

A 2.32 6CB &.52 6CC 3.5: 6C

D 5&.,5 6C

"3. !he following e0uation shows a reaction.

C)p+; '2)g+ C'2)g+ = - > &6.6 1 mol5

Calculate the mass of carbon needed to release :.6 1 of heat for the reaction.G elative atomic mass C52< '5,< -5 H

A 6.2 gB 2.& gC ".2 gD (., g

&6. !he combustion of 5.,g of methanol increase the temperature of 2(6 cm"of water by"& 6C. Calculate the increase in temperature of (66cm"of water from the combustionof ".2g of methanol.

A 5./6

CB ".& 6CC 5/.6 6CD "&.6 6C

&5. !he following e0uation shows a reaction.

C-&)g+; 2'2)g+ C'2)g+ ; 2-2')l+ =- > 366 1 mol@5

Calculate the heat released when &g of methane C-&is completely burnt in oygen.

G elative atomic mass -5< C52 H

A 22.( 1B 22( 1C ",6 1D ",66 1

&2. !he following shows an ionic e0uation for a reaction.

Pb2;)a0+; 8'&2

)a0+ Pb8'&)s+ =-> (6.& 1 mol@5

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Calculate the change in temperature when lead)**+ sulphate Pb8'& is precipitate from

the reaction of (6 cm" of 5 mol dm"lead)**+ nitrate solution Pb)$'"+2 and (6 cm"of 5

mol cm" sodium sulphate solution $a28'&

G 8pecific heat capacity of water> &.2 g5 6C5H

A 6., 6C

B ,.6 6CC 5.2 6CD 52.6 6C

&". !he following e0uation shows a reaction.

Fn)s+; Cu8'&)a0+ Fn8'&)a0+; Cu)s+ = ->25/ 1 mol@5

#cess %inc powder is added into 52( cm"of 6.5 mol dm" copper)**+ sulphate

solutionCu8'& Calculate the rise in the temperature of the miture.

G 8pecific heat capacity of solution > &.2 g5 6

C5

H

A 6.( 6CB 5.: 6CC &.5 6CD (.2 6C

&&. !he following e0uation shows a reaction.

C)s+ ; 62)g+E C'2)g+< = - > @"3& 1 mol@5

Based on the above e0uationwhat is the heat released when (g of carbon iscompletely burnt in oygen?

G elative atomic mass C52 < '5, H

A 5,&.2 1B /::.6 1C 3&(., 1D 5 3/6.6 1

&(. !he following e0uation shows a reaction.

8)s+; '2)g+E 8'2)g+ < = - > @"66 1 mol@5

Based on the above e0uation which of the following pairs of sulphur and oygen doesnot released "66 1 of heat?Gelative atomic mass ' 5, < 8 "2H

A "2g sulphur and 5,g oygenB "2g sulphur and "2g oygenC ,&g suphur and "2g oygenD "2g sulphur and ,&g oygen

&,. !he following ionic e0uation shows a reaction.

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Pb2;)a0+; 8'&2@)a0+ E Pb8'&)s+ < = - > @(6.& 1 mol@5

Based on the above e0uation determine the highest temperature obtained when(6 cm" of 6.( mol dm@"lead)**+ nitrate solution is mied with (6 cm" of 5.6 mol dm@"potassium sulphate solution if the initial temperature is "6 6C.G8pecific heat capacity of water > &.2 g @56CH

A 2&6

CB 2/ 6CC "" 6CD ", 6C

&/. Iour mitures W J and F are obtained by miing 5.6 mol dm@"of sodium hydroidesolution with 5.6 mol dm@" of sulphuric acid. Which of the following mitures provide thehighest rise in temperature?

4iture7olume of 5 mol dm@"of

sodium hydroidesolution )cm"+

7olume of 5 mol dm@"ofsulphuric acid

)cm"+

A W 26 26B J &6 26

C 26 &6

D F &6 &6

&:. Which of the following pairs of solutions produce the highest rise in temperature when

they are mied?

A 2( cm" of 6.5 mol dm@" sodium chloride and 2(cm" of 6.5 mol dm@" silver nitratesolution

B (6 cm" of 6.5 mol dm@" sodium chloride and (6 cm" of 6.5 mol dm@" silver nitratesolution

C 2( cm" of 6.2 mol dm@" sodium chloride and 2(cm" of 6.2 mol dm@" silver nitratesolution

D 2( cm"of 6.5 mol dm@"barium chloride solution and 2( cm"of 6.2 mol dm@" silvernitrate solution

&3. !he heat of combustion of glucose is @2 /"6 1 mol@5. Calculate the mass of glucoseneeded to burn in a calorimeter bom if the heat released increase the temperature of(66 cm" of water by 5" 6C?G elative molecular mass glucose5:6< 8pecific heat capacity of water> &.2 g@5 6C@5H

A 5.: gB 56.6 gC 366.6 gD 5 :66.6g

(6. !he heat of combustion of ethanol is @5 "(6 1 mol@5. Calculate the mass of ethanolburnt if 5(6 cm"of water is boiled. !he initial temperature of water is 2( 6C .Gelative molecular mass ethanol &, < 8pecific heat capacity of water > &.2 g @5 6C@5H

A 6.6"(gB 6.(&6gC 6./,6g

D 5.,56g

Paper 2

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Section AG,6 marksH

Answer all questions in this section.The time suggested to complete this section is 90 minutes

5. Diagram 5 shows the set up of the apparatus to determine the heat of combustion

of ethanol. !hermometer

Wind shield copper can

water

!ripod stand

8pirit lamp #thanol

Diagram 5

!he following data is obtained

4ass of lamp ; ethanol before burning > 2".&6 g4ass of lamp ; ethanol after burning > 25.56 g7olume of water > &66 cm"

*nitial temperature of water > 2:.6 6C-ighest temperature of water > ,,.6 6C

G 8pecific heat capacity of water > &.2 g6C< water density > 5 g cm"H

Based on Diagram 5 answer the following 0uestions.

a+ Why is copper can used in the eperiment?

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(Knowledge)

b+ Write the e0uation for the combustion of ethanol with ecess oygen.

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(Understanding)

c+ Based on the results obtained calculate

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i+ the heat releasedin the eperiment

G5 markH

(Aplication)

ii+ the number of moles of ethanol burnt

G5 markH(Aplication)

iii+ the heat of combustion of ethanol

G2 marksH(Aplication)

d+ Draw the energy level diaram for the combustion of ethanol

G2 marksH (Synthesis)

e+ *s the value of the heat of combustion of ethanol C2-('- obtained in the

eperiment the same as the theoretical value ? #plain

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KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK.G" marksH

(Aplication)

f+ *s the heat of combustion of propanol is higher than ethanol? #plain.

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KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK. G2 marksH

(Understanding)

2. An eperiment is carried out to determine the heat of displacement for the reaction

between copper )**+ sulphate solution and ecess %inc powder. (6.6 cm"of 6.( mol dm"

copper )**+ sulphate solution is poured into a plastic cup. !he initial temperature of thesolution is recorded. #cess %inc powder is added into a plastic cup. !he miture isstirred and the highest temperature is recorded.


*nitial temperature of copper )**+ sulphate solution > 2:.( 6C-ighest temperature of the miture > "".( 6C

G elative atomic mass Cu,&< 8"2< '5,< Fn ,(< 8pecific heat capacity

of water &.2 g56C5H

a+ What is meant by the heat of displacement based on the eperiment?

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(Knowledge)

b+ Write an ionic e0uation for the reaction of the eperiment.

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(Understanding)

c+ 8tate two observations in the eperiment.

i+ KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK

ii+ KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK G5 mar1H

(Analyse)

d+ Calculate

i+ the heat released

G5 markH (Aplication)

ii+ the number of moles of copper )**+ sulphate reacted

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G5 markH

(Aplication)

iii+ the heat of displacement

G5 markH (Aplication)

e+ Why is %inc used in this eperiment is in powder form?

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(Understanding)

f+ Draw the energy level diagram for the reaction in this eperiment.

G2 markH(Syntesis)

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". Diagram 2 shows the energy level diagram for the reaction between strong acid andstrong al1ali. !he heat of of neutrali%ation for the reaction in #periment * is

(/ 1 mol5.

#nergy

-;)a0+; '-

)a0+

-> (/ 1 mol5

-2')l+

Diagram 2a+ $ame one eample of strong asid and strong al1ali.

i+ 8trong acidKKKKKKKKKKKKKKKKKKKKKKKKKKKK

ii+ 8trong al1aliKKKKKKKKKKKKKKKKKKKKKKKKKKK..

G2 markH (Knowledge)

b+ What is meant of heat of neutrali%ation?

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KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK

G5 markH (Knowledge)

%7 An eperiment )eperiment **+ is carried out under the same condition that is (6

cm"of 5 mol dm"of ethanoic acid is mied with (6 cm"of 5 mol dm" strong

al1ali. !he temperature of the miture is increased by ,.( 6C.

i+ Calculate the number of moles for strong al1ali used.

G5 markH (Understanding)

ii+ Calculate the heat of neutrali%ation between ethanoic acid with strong al1ali.

Gspecific heat capacity of solution > &.2 g5 6C5 5 g cm"H

G5 markH (Understanding)

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d+ i+ Compare the heat of neutrali%ation for #periment * and #periment **

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G5 markH (Analysis)

ii+ #plain your answer.

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KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKG2 marksH

(Analysis)

e+ *f #periment ** is repeated by miing 566 cm"of 5 mol dm"ethanoic acid with 5

moldm"of strong al1ali with the same concentration the temperature increased isstill ,.( 6C. #plain.

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KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK G" marksH

(Synthesis)

&. 2( cm" of 6.( mol dm"barium chloride solution is measured by using a mesuring

cylinder and poured into a polystyrene cup. !he initial temperature is recorded. !hen

2( cm"

of 6.( mol dm"

sodium sulphate solution is measured and the initialtemperature is recorded. 8odium sulphate solution is poured into barium chloridesolution. !he miture is stirred and the highest temperature is recorded.


*nitial temperature of barium chloride solution > 2:.6 6C*nitial temperature of sodium sulphate solution > 2:.6 6C-ighest temperature of the miture > "5.6 6C

G8pecific heat capacity > &.2 g5 6C5H

a+ What is the colour of barium sulphate precipitate?

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(Knowledge)

b+ Calculate

i+ the number of moles of barium ion

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Section BG26 marksH

Answer any onequestion.The time suggested to answer this section is 30 minutes.

5. Diagram " shows the energy level diagram for a reaction between nitrogen and oygengas.

#nergy 2$'2)g+

=- > ;,, 1 mol5

$2)g+ ; '2)g+

Diagram "

)a+ #plain how the energy changes during the brea1ing and formation of bond in thereaction based on the value of = - itu.

G, marksH Understanding

#periment Procedure!emperature changes of

the miture

*

**

4iing 2(cm" of 5.6 moldm"sodium

hydroide solution with 2(cm"of 5.6

moldm"nitric acid in a plastic bea1er.

4iing 2(cm" of 5.6 moldm"sodiumhydroide solution with 2(cm"of 5.6

moldm"methanoic acid in a plastic

bea1er.

!emperature is increasedby ,./(oC

!emperature is increasedby ,."6oC

!able 5

2. )b+ i+ Based on the result of the eperiment shown in table 5 calculate the heat ofneutrali%ation for #periment * and #periment **.

G8pecific heat capacity of the solution > &.2 g5oC5H

G56 marksH Aplication

ii+ Compare the values of the heat of neutrali%ation in b)i+. #plain.

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G& marksH Analysis

Section CG26 marksH

Answer any onequestion.The time suggested to answer this section is 30 minutes.

5. )a+ !he following e0uations represent neutrali%ation reactions.

eaction *

-Cl)a0+; $a'-)a0+ $aCl)a0+; -2')l+ = - > J 1 mol5

eaction **

C-"C''-)a0+; $a'-)a0+ C-"C''-$a)a0+ ;-2')l+ = - > 1 mol5

!he heat of neutrali%ation for both reactions are different. 8tate the differences andeplain.

G& marksH

)b+ Diagram & shows the energy level diagram of a reaction. #nergy

Ag;; Cl

- > negative

AgCl

Diagram &

i+ $ame the reactants involved.G2 marksH

ii+ Write the chemical e0uation for the reaction. G5 markH

iii+ What is the assumption made in calculating the heat of precipitation in thiseperiment.

G2 marksH

)c+ Describe an eperiment to determine the heat of neutrali%ation of sulphuric acid-28'&with pottassium hydroide solution '-. our eplaination should include

chemical e0uation for the reaction calculations involved and precautions in gettinga more accurate results.

G56 marksH

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Paper 3

Answer allquestion in this section

5. Diagram 5 shows the set up of the apparatus to determine the heat of displacement ofiron by magnesium metal.

Displacement of iron by magnesium occurs as shown in the e0uation below

4g ; Ie8'& 4g8'&; Ie

a+ i+ Based on the information in diagram 5 complete the table

*nitial temperature of iron )**+ sulphate solution)oC+

-ighest temperature of iron )**+ sulphate

solution)

o

C+

iii+ 8tate the type of reaction that occurs?

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b+ 8tate one observation in the eperiment.

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22

Initi! te#er!tureHigest te#er!ture

Teroeter

e!suring /otte

9%ess !gnesiu

#ow$er

166%3

iron ;II7

su#!te

soution

stir

&i!gr! 1


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!able 2 shows the results obtained from the eperiment.

Alcohol$umber of carbon atoms per

alcohol molecule-eat of combustion of

alcohol )1 molL5+

4ethanol C-"'- 5 L/5&

#thanol C2-('- 2 L5"(&Propan@5@ol C"-/'- "

Butan@5@ol C&-&'- & L2(,&

a+ i+ Draw a graph of the heat of combustion of alcohol against the number of carbonatoms per alcohol molecule.

iii+ Based on the graph determine the heat of combustion of propanol.

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b+ 8tate the variables for the eperiment.

i+ esponding variable

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ii+ 4anipulated variable


iii+ Constant variable


c+ 8tate the hypothesis for the eperiment.


d+ What is the relationship between the number of carbon atoms with the value ofthe heat of combustion of alcohols


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!he following information shows the heat of combustion of two types of alcohols.Plan an eperiment to compare the heat of combustion of the alcohols. our planning shouldinclude the following aspects.

)a+ Problem statement)b+ All the variables

)c+ statement of the hypothesis)d+ 9ist of substances and apparatus

)d+ Procedure of the eperiment)e+ !abulation of data.

G5/ markH

Heat of combustion of ethanol = - 1376 kJ mol-1

Heat of combustion of propan- 1- ol = - 2016 kJ mol-1

(13)thermochemistry

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