MODULEJPN CHAPTER13

8/7/2019 MODULEJPN CHAPTER13

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CHAPTER 13: THERMOCHEMISTRYSECTION A: Common Mistake Made By The Candidates

1. Students have misunderstanding the concept of exothermic and endothermicreaction.

Example: What is the meaning of endothermic and exothermic reaction?Incorrect;

Endothermic reaction;

Reaction that involves release of energy to the surroundings which increases the

temperature of the system.Exothermic reaction;

Reaction that involves absorb of energy from surroundings which decrease the

temperature of the system.

Correct;Exothermic reaction;

Reaction that involves release of energy to the surroundings which increases the

temperature of the system.Endothermic reaction;

Reaction that involves absorb of energy from surroundings which decrease thetemperature of the system.

2. students are not able to differentiate between heat release during the reaction and

heat energy.

Example: In the experiment, excess zinc powder is added to 25cm3 of 0.2mol/dm3

copper(ll) sulphate. The temperature rises by 8oC. Calculate the heat changes in

the reaction.Incorrect: mc = 25(4.2)8 = 840 joules

Correct: mc = 25(4.2)8 = 840 joules

0.005mol of copper(ll) sulphate produce 840 joules of energy,

thus, 1 mol of copper(ll) sulphate produce 840 = 168000 joules0.005

1 | P a g e T h e r m o c h e m i s t r y


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SECTION B: DIAGNOSTIC QUESTIONS

a) Objective Questions

1. What is the meaning of endothermic reaction?

Apakah yang dimaksudkan dengan tindakbalas endotermik?

A. Reaction when 1 mol of reactant is reacted and changed into product.

Tindakbalals apabila 1 mol bahan bertindakbalas dan ditukarkan kepadahasil.

B. Reaction that involves the absorption of energy from the surroundings.Tindakbalas yang melibatkan penyerapan tenaga daripada persekitaran.

C. Reaction when 1 mol of water is formed from reaction between acid and

alkali.

Tindakbalas apabila 1 mol air terbentuk daripada tindakbalas di antara asiddan alkali.

D. Reaction that involves release of energy to the surroundings whichincreases the temperature of the system.

Tindakbalas yang melibatkan pembebasan tenaga ke persekitaran yangmeningkatkan suhu kepada sistem

2. Which of the following is not true about exothermic reaction?Yang manakah antara yang berikut tidak betul mengenai tindakbalas

eksotermik?

A. Heat of reaction, H, has a positive valueTindakbalas pemanasan, H mempunyai nilai positif

B. Heat is liberated to the surrounding system.Haba dibebaskan ke system persekitaran

C. The product of reaction has lower energy than the reactant.Hasil tindakbalas mempunyai tenaga yang rendah berbanding dengan hasil.

D. Heat release from the formation of bond exceed heat absorbed for thebreaking of chemical bonds.Haba yang dibebaskan daripada pembentukan ikatan melebihi haba yang

diserap untuk pemecahan ikatan kimia.



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3. What does heat of precipitation means?Apakah yang dimaksudkan haba pemendakan?

A. The heat of reaction when 1 mol of precipitate is reacted.

Haba tindakbalas apabila 1 mol mendakan ditindakbalaskan.

B. The heat release that exceeds the heat absorbed for the reaction,

Haba yang dibebaskan melebihi haba yang diserap untuk tindakbalas.

C. The heat of reaction when 1 mol of precipitate is formed from its

respective ions.Haba tindakbalas apabila 1 mol mendakan terbentuk daripada ion masing-

masing.

D. The heat of reaction when 1 mol of metal is displace from its salt solution

by other more electropositive metal under standard conditions.

Haba tindakbalas apabila 1 mol logam disesarkan daripada larugaramnya oleh logam yang lebih keelektropositifan di bawah keadaanpiawai.

4. When 50cm3 of silver nitrate solution 0.1 mol/dm3 reacts with the 50cm3 of

sodium chloride solution, 0.1 mol/dm3, the following energy level diagram isobtained.Apabila 50cm3 larutan argentum nitrat 0.1mol/dm3 ditindakbalaskan dengan

50cm3 larutan natrium klorida 0.1mol/dm3, gambarajah aras tenaga dibawah

diperolehi.

energy

Ag+ (aq) + Cl- (aq)

H=-52 kJ/ mol

AgCl (p)

Based on the above diagram, which of the following are true?

Berdasarkan diagram di atas, yang mananakah dia antara berikut benar?

l the heat of precipitation is -52kJ/mol

haba pemendakan ialah -52kJ/mol.

ll from the experiment, 0.5 mol of precipitate is formed.Daripada eksperimen, 0.5 mol mendakan terbentuk.



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lll The product have higher energy level than the reactants .hasil tindakbalas mempunyai aras tenaga yang lebih tinggi berbanding

dengan bahan tindakbalas.

lV 260 J of energy is released when two solutions are mixed together.

260 J tenaga dibebaakan apabila dua larutan ini dicampurkan bersama.

A l and lV only

B. l, ll,and lll only

C. l. lll dan lV onlyD. ll, lll dan 11l only

5. Which of the following equations represents a neutralization reaction?Yang manakah persamaan dibawah mewakili tindakbalas peneutralan?

A. NaOH + HCl H2O + NaCl

B. ZnCl + Mg MgCl2 + Zn

C. AgNO3 + KCl AgCl + KNO3

D. Na2CO3 + 2HCl 2NaCl + H2O +CO2

6. Why is the heat released in the reaction between a weak acid and strong alkali islesser than that in the reaction between a strong acid and strong alkali?Mengapakah haba yang terbebas dalam tindakbalas di antara asid lemah dan

alkali kuat lebih rendah berbanding tindakbalas di antara asid kuat dan alkali

kuat?

A. Heat is lost to surroundingsHaba hilang ke persekitaran

B. Weak acid dissociate partially in water.Asid lemah mengion separa di dalam air.

C. Heat released is absorbed to complete the dissociation of weak acidHaba yang dibebaskan diserap untuk perceraian lengkap dalam asid lemah.

D. The reaction between a weak acid and strong alkali is slow..Tindakbalas di antara asid lemah dengan alkali kuat adalah perlahan.



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7. The heat liberated when 1 mole of fossil burnt completely in excess oxygen.

What type of energy change the statement refers to?Haba dibebaskan apabila 1 mol bahan api dibakar lengkap dalam oksigen yang

berlebihan. Apakah jenis tenaga yang dimaksudkan oleh pernyataan tersebut?

A. Heat of precipitationHaba pemendakan

B. Heat of neutralizationHaba peneutralan

C. Heat of combustionHaba pembakaran

D. Heat of displacement.Haba penyesaran.

8. When excess magnesium powder is added into 100cm3of 0.5mol/dm3 iron(ll)

chloride, the temperature increases from 30oC to 54oC. What is the heat ofdisplacement of iron? (specific heat capacity of the solution = 4.2 g-1

oC-1. ;

density of solution = 1 g/dm3)Apabila serbuk magnesium yang berlebihan ditambahkan kepada 100cm3 larutan

ferum(ll) klorida 0.5mol/dm3, haba meningka naik daripada 30oC kepada 54oC .

berapakah haba penyesaran ferum ?

A. -108.0kJ/mol

B. -184.5 kJ/mol

C. -201.6 kJ/mol

D. -240.0 kJ/mol



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9. Z displaces Y from XY. The energy change of the reaction is shown in the energy

level diagram below.Z menyesarkan Y daripada XY. Perubahan tenaga tindakbalas adalah merujuk

kepada gambarajah aras tenaga dibawah

Which of the following statements is true?

Yang manakah pernyataan dibawah adalah betul?

A. It is an endothermic reactionIni adalah tindakbalas endotermik

B. The products have more energy than the reactantsHasil mempunyai tenaga yang lebih banyak berbanding dengan hasil

C. The temperature change of the reaction has a negative valuePerubahan suhu dalamtindakbalas mrmpunyai nilai negative

D. The heat released from bond making is greater than that in bond

breakingHaba yang dibebaskan daripada pembentukan ikatan lebih tinggi berbanding

dengan haba pemecahan

10. 0.32g of etanol, C2H5. is burnt completely in excess oxygen. The energy released

increase the temperature of 100cm3 water by oC . What is the heat of combustion

for etanol ? (RAM C=14, H=1)0.32g etanol, C2H5, di bakar lengkap dalam oksigen yang berlebihan. Tenaga

yang dibebaskan meningkatkan suhu air 100cm3 sebanyak XoC. Apakah habapembakaran untuk etanol ? (RAM C=14, H=1)

A. 8618. kJ/mol

B. 1086.8 kJ/mol

C. 108.68 kJ/mol


energy


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D. 861.81 kJ/mol

b) Subjective Questions

Experiment 1

Initial temperature of solution: highest temperature of mixt

Experiment 2

Initial temperature of solution: .. highest temperature of mixtu

Complete the reading of temperature aboveLengkapkan bacaan thermometer di atas

Based on diagram above, state the type of reaction for each experiment, exothermic or

endothermic reaction?Berdasarkan gambarajah di atas, nyatakan jenis tindakbalas untuk setiap eksperimen,

eksotermik atau endotermik

...

What do exothermic and endothermic reaction mean?Apakah yang dimaksudkan dengan tindakbalas eksotermik dan endotermik?

...

...


25o C 35o C

25o C 20o C

30

20

30

20

30

20

30

20


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Based on information above, complete the table below.

Lengkapkan jadual dibawah

Experiment

Eksperimen

Initial

temperatureSuhu awal

Maximum

temperatureSuhu

maksimum

Changes in temperature

Perubahan suhu

Type of

reactionJenis tindak

balas

1 W1 W2

W1 >W2

( temperature drop)( suhu menurun )

2 X1 X2X1 >X2

( temperature rises)

( suhu menungkat )..

3 Y1 Y2 Y1 >Y2( temperature rises)

( suhu menungkat )

(a)Base onenerg

y

level

diagram

abov

e,identi

fy the

exothermic

and

endot

herm

Z1 Z2

Z1 >Z2

( temperature drop)( suhu menurun )

..


Exothermic reaction: Endothermic reaction:

Heat is given off to surrounding Heat is absorbed fro

surroundingTemperature of surrounding increase temperature of surrounding decrease


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ic

react

ion.4

Berdasarkangambarajah

aras tenagadi atas,kenalpasti

tindakbalas

eksotermikdan

endotermik.

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

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

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

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

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

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

(b)State the characteristic of exothermic and endothermic reaction.50 cm3 of 1.0mol/dm3 calcium nitrate solution is added to 50cm3 of 1.0mol/dm3 sodium

carbonate solution in a polystyrene cup in an experiment to determine the heat of precipitation

of calcium carbonate. The results of the experiments are shown below.

50 cm3 larutan kalsium nitrat 1.0mol/dm3 ditambahkan kepada 50 cm3 larutan natriumkarbonat 1.0mol/dm3 didalam cawan polysterin dalam eksperimen menentukan haba

pemendakan kalsium karbonat. Keputusan daripada eksperimen adalah seperti yangditunjukkan di bawah.

Initial temperature of calcium nitrate solution = 30oC

Suhu awal larutan kalsium nitrat

Initial temperature of sodium carbonate solution = 28oCSuhu awal larutan natrium karbonat

Highest temperature of mixture = 35oCSuhu tertinggi campuran

What is heat of precipitation?Apakah haba pemendakan?

...



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Calculate the temperature change of the reaction.Kirakan perubahan suhu dalam tindakbalas.

Is this reaction exothermic or endothermic reaction ?Adakah tindakbalas di atas tindakbalas eksotermik atau endotermik ?

...

An excess of zinc powder is added to 25cm3 of copper(ll) sulphate 0.1 mol/dm3 to determine

the heat of displacement for the reaction. The temperature rises from 30oC to 38oC.Serbuk zink berlebihan ditambahkan kepada 25cm3 kuprum sulfat 0.1mol/dm3

menentukan haba penyesaran bagi tindakbalas. Suhu meningkat daripada 30oC kepada38oC.

What is heat of displacement?Apakah haba pemendakan?

...

Calculate the temperature change of the reactionKirakan perubahan suhu dalam tindakbalas.

...

Write the ionic equation for the reaction above.Tuliskan persamaan ion untuk tindak balas di atas.

...

Calculate the number of mole of copper(ll) sulphate ?.

Kirakan bilangan mol kuprum(ll) sulfat.

Neutralization reaction occurs when 50cm3 of 0.5mol/dm3 sulphuric acid react with 25cm3 of2 mol/dm3 sodium hydroxide. The temperature rises by 8oC in the reaction mixture.

Tindakbalas peneutralan terjadi apabila 50cm3 asid sulfuric 0.5mol/dm3 bertindakbalasdengan 25cm3 natrium hidroksida 2mol/dm3. suhu meningkat sebanyak 8oC dalam campuran

tindakbalas.

10 | P a g eT h e r m o c h e m i s t r y


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Define the term heat of neutralization.Nyatakan definisi haba peneutralan.

...

Calculate the heat changes in the reaction

Kirakan perubahan haba dalam tindakbalas.

...

Write the chemical equation of the reaction.

Tuliskan persamaan kimia bagi tindakbalas

...

If the acid used in the reaction is replace by ethanoic acid, what is the value of heat ofneutralization? Explain your answer.Jika asid yang digunakan dalam tindakbalas digantikan dengan asid etanoik, apakah

nilai haba peneutralan ? Jelaskan jawapan anda.

...

...

...

SECTION C: PAPER 2

a) Structured Question:



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A student carried out an experiment to determine the heat of displacement of copper for the

reaction between zinc and copper(ll) sulphate solution. In this experiment, excess zin

powder is added to 25cm3 of 0.2mol/dm3 copper(ll) sulphate solution in a plastic cup. Thtemperatures of copper(ll) sulphate solution before and after the addition of zinc powder ar

recorded

Initial temperature of copper sulphate solution = 28oC

The highest temperature of the solution after the addition of zinc = 37.5 oC

(specific heat capacity of the solution, 4.2 Jg-1oC; the density of the solution, 1 gcm-3)

Seorang pelajar menjalankan satu eksperimen untuk menentukan haba penyesaran kuprum

bagi tindakbalas di antara zinc dan larutan kuprum sulfat. Dalam eksperimen ini serbuk zink

berlebihan ditambahkan kepada 25cm3 of 0.2mol/dm3 larutan kuprum sulfat dalam cawan

plastik. Suhu larutan kuprum sulfat sebelum dan selepas penambahan serbuk zink dicatatkan;

Suhu awal larutan kuprum sulfat = 28

o

CSuhu tertinggi larutan selepas penambahan zinc = 37.5oC

( Muatan haba tentu bagi larutan, 4.2 Jg-1oC; ketumpatan larutan, 1 gcm-3 )



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What is meant by heat of displacement ?Apakah yang dimaksudkan dengan haba penyesaran?

_______________________________________________________________________

_______________________________________________________________________[1 mark]

What is the colour change of the copper(ll) sulphate solution in this reaction?Apakah perubahan warna larutan kuprum sulfat dalam tindakbalas ini?

_______________________________________________________________________

[1 mark]

Write an ionic equation for the reaction.Tuliskan persamaan ion untuk tindakbalas ini

_______________________________________________________________________

[1 mark]

Based on the results of this experiment, calculateBerdasarkan keputusan eksperimen ini, kirakan

(i) The number of mole of copper(ll) ions displaced.Bilangan ion kuprum yang dinyahcaskan.

[2 marks]

(ii) The heat given out in this reaction.

Haba yang dibebaskan dalam eksperimen ini.

[2 marks]

(iii) The heat of displacement of copper in this reaction.Haba penyesaran kuprum dalam tindakbalas ini.



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[2 marks]

Draw an energy level diagram for the reaction.Lukis gambarajah aras tenaga untuk tindakbalas ini.

[2 marks]

b) Essay Question

Define exothermic and endothermic reactions. Give one example each for exothermic

and endothermic reactions.Takrifkan tindakbalas eksotermik dan endotermik. Berikan satu contoh bagi setia

tindakbalas eksotermik dan endotermik.

[4 marks]

Design an experiment to determine the heat of precipitation for the reaction betweenbarium nitrate solution and potassium sulphate solution. Include set up of apparatus

equation, and calculation to determine the heat of precipitation.Rancangkan satu eksperimen untuk menentukah tindakbalas haba pemendakan di

antara barium nitrat dengan potassium sulfat. Masukkan set peralatan, gambarajah,

persamaan dan pengiraan dalam menentukan tindakbalas haba pemendakan.

[16 marks]

SECTION D: PAPER 3:

The table shows the heat of combustion of several alcohols.Jadual menunjukkan haba pembakaran bagi beberapa alkohol.

Alcohol

Alkohol

Heat of combustion ( kJ/mol)

Haba Pembakaran ( kJ/mol)

Methanol -725

Ethanol -1376



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Propanol -2015

Design an experiment to compare the heat of combustion for the alcohol in the table

above. In designing your experiment, it must include the following items;Rancangkan satu eksperimen untuk membandingkan haba pembakaran alcohol dalam

jadual di atas. Dalam eksperimen tersebut, masukkan item-item yang berikut:

a) problem statement

pernyataan masalah

b) hypothesishipotesis

c) list of substances and apparatussenarai bahan dan radas

d) procedurekaedah

e) tabulation of data

penjadualan data

[17 marks]Nyatakan ciri-ciri tindakbalas eksotermik dan endotermik

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

energy energy

reactants product

H is negative H is positive

products reactants


Energy Level Diagram A

Gambarajah Aras Tenaga A

Energy Level Diagram B

Gambarajah Aras Tenaga B


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3.


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MODULEJPN CHAPTER13