4. THERMOCHEMISTRY

SET 710 (a) An experiment has done to determine the heat of neutralisation between hydrochloric acid solution with

sodium hydroxide solution.Table 10.1 below shows the information of the experiment.Satu eksperimen dijalankan untuk menentukan haba peneutralan antara larutan asid hidrokorik dengan larutan natrium hidroksida.Jadual 10.1 menunjukkan maklumat bagi eksperimen tersebut.

Total volume of mixture of hydrochloric acid solution and sodium hydroxide solutionJumlah isipadu campuran antara larutan natrium hidroksida dan larutan asid hidroklorik

100 cm3

Temperature change when sodium hydroxide solution is added into hydrochloric acid solutionPerubahan suhu apabila larutan natrium hidroksida di tambah kepada larutan asid hidroklorik

6.8 oC

Number of mole of water formedBilangan mol air yang terbentuk 0.05 mol

Table / Jadual 10.1

(i) Calculate the heat released from the neutralisation reaction above.Hitungkan haba yang dibebaskan oleh tindak balas peneutralan di atas.

[Given / Diberi : Heat released / Haba terbebas = mcθ ; c = 4 J g-1 oC-1 ] [1 mark]

(ii) Calculate the heat of neutralisation for above experiment.Hitungkan haba peneutralan bagi eksperimen di atas. [2 marks]

(iii) Draw the energy level diagram for above experiment.Lukiskan gambar rajah aras tenaga bagi eksperimen di atas. [2 marks]

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(b) Table 10.2 shows the heat of neutralisation for Experiment I, II, and III.Jadual 10.2 menunjukkan haba peneutralan bagi Ekperimen I, II dan III.

ExperimentEksperimen

Neutralisation reaction betweenTindak balas peneutralan antara

Heat of neutralisation (kJ mol-1) Haba peneutralan (kJ mol-1)

IHydrochloric acid with sodium hydroxideAsid hidroklorik dengan kalium hidroksida

- 57

IINitric acid with sodium hydroxideAsid nitrik dengan natrium hidroksida

- 57

IIIEthanoic acid with sodium hydroxideAsid etanoik dengan natrium hidroksida

- 55

Table / Jadual 10.2

(i) Write the ionic equations and explain why the heat of neutralisation for Experiment I and II are the same.Dengan menulis persamaan ion terangkan mengapa haba peneutralan Eksperimen I dan II sama nilainya.

[2 marks]

(ii) Explain why the heat of neutralisation for Experiment I and II are different.Terangkan mengapa haba peneutralan bagi Eksperimen I dan III adalah berbeza.

[3 marks]

(c)

By using materials above, describe a laboratory experiment to determine the heat of displacement of copper. Your description should include :Dengan menggunakan bahan di atas, huraikan satu eksperimen makmal untuk menentukan haba penyesaran kuprum. Penerangan anda mestilah mengandungi :

procedures of the experimentlangkah-langkah eksperimen

persamaan tindak balaschemical equation for the reaction

calculation steps to determine the heat of displacement.langkah-langkah penghitungan untuk menentukan haba penyesaran.

[10 marks]

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20 cm3 of 0.2 mol dm-3 copper(II) sulphate solution 20 cm3 larutan kuprum(II) sulfat 0.2 mol dm-3

Zinc powderSerbuk zink

set 85 Figure 5 is an energy level diagram for neutralization reaction of hydrochloric acid with sodium

hydroxide.Rajah 5 ialah gambar rajah aras tenaga bagi tindak balas peneutralan antara asid hidroklorik dengan larutan natrium hidroksida.

Energy /Tenaga HCl + NaOH

H = -57 kJ mol-1

NaCl + H2O

FIGURE / RAJAH 5

(a) H is heat of reaction of neutralization reaction. What is represented by H = -57 kJ mol -1 for the reaction aboveH adalah haba tindak balas bagi tindak balas peneutralan.Apakah yang diwakili oleh H = -57 kJ mol -1 bagi tindak balas di atas ?

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

...................................................................................................................................................... [ 2 markah](b) Write ionic equation for the reaction above

Tuliskan persamaan ion untuk tindak balas di atas.

..................................................................................................................................................... [ 1 markah](c) State the type of form bonding thet cause the changing above

Nyatakan jenis ikatan yang terbentuk yang menyebabkan perubahan di atas.

......................................................................................................................................................[ 1 markah](d) Experimen to determine the neutralisation heat above is conducted when 100 cm3 hydrochloric acid 1.0

mol dm-3 and 100 cm3 sodium hydroxide solution 1.0 mol dm-3 all together is poured into the different plastic beaker. The initial temperature of hydrochloric acid and sodium hydroxide is recorded. Then, sodium hydroxide solution is poured into the plastic cup that contain hydrochloric acid, the mixture is stirred slowly and the highest temperature is recorded.Eksperimen untuk menentukan haba peneutralan di atas dijalankan apabila 100 cm3 asid hidroklorik 1.0 mol dm-3 dan 100 cm3 larutan natrium hidroksida 1.0 mol dm-3 masing-masing dituangkan ke dalam bikar plastik yang berasingan. Suhu awal asid hidroklorik dan larutan natrium hidroksida dicatat. Kemudian larutan natrium hidroksida dituang ke dalam cawan plastik yang mengandungi asid hidroklorik. Campuran dikacau perlahan-lahan dan suhu tertinggi dicatatkan.

Calculate / Hitungkan :

(i) the number of mol of hydrochloric acid that is used in the experiment bilangan mol asid hidroklorik yang digunakan dalam eksperimen ini.

[ 1 markah]

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(ii) The changing of heat in the experimentperubahan haba dalam eksperimen ini.

[ 1 markah](iii) Assume the changing temperature that will occur in the experiment

perubahan suhu yang dijangkakan dalam eksperimen ini.[Latent heat / Muatan haba tentu larutan = 4.2 J g-1 oC-1 ]

[ 1 markah ]

(e) Neutralisation heat for the reaction between ethanoic acid and sodium hydroxide is lower than the neutralization between hydrochloric acid and sodium hydroxide. Explain.

Haba peneutralan bagi tindak balas antara asid etanoik dengan larutan natrium hidroksida adalah lebih rendah berbanding haba peneutralan antara asid hidroklorik dengan larutan natrium hidroksida. Terangkan.

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

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

............................................................................................................................................................. [ 3 markah]

set3 p32 A student carried out an experiment to determine the heat of displacement of copper.50cm3 of 0.5moldm-3

copper(II) sulphate solution is poured into a polystryne cup. The initial temperature of the solution is recorded. An excess zinc powder is then added into the polystyrene cup and is stirred as shown in diagram 2.1.Seorang pelajar telah menjalankan eksperimen untuk menentukan haba penyesaran kuprum. 50 cm3 larutan kuprum(II) sulfat 0.5 mol dm-3 dimasukkan ke dalam cawan polistirena.. Suhu awal larutan dicatatkan. Kemudian serbuk zink berlebihan ditambah ke dalamcawan polistirena dan dikacau seperti Rajah 2.1

Diagram 2.1 RAJAH 2.1

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Copper (II)sulphate solutionLarutan Kuprum(II)sulfat

thermometertermometer

polystyrene cupCawan polisterena

Zinc granulesKetulan zinkBeginning of experiment

Awal eksperimenEnd of ExperimentAkhir eksperimen

The initial and maximum temperature of thermometer is recorded as shown in diagram 2.2.Suhu awal dan suhu maksimum termometer telah direkodkan seperti Rajah 2.2

Initial temperature Maximum temperatureSuhu awal Suhu maksimum

RAJAH 2.2

(a) State three observations in this experiment Nyatakan tiga pemerhatian dalam eksperimen ini.

……………………………………………………………..………………………………………..

……………………….………………………………………………………………………………

…………….………………………………………………………………………[ 3 marks ]

(b) Reffering to Diagram 2.2, determine the temperature below :Merujuk kepada Rajah 2.2, tentukan nilai suhu berikut:

Initial Temperature : .........................................................................................................Suhu awal : ………………….…………………..………………………………………..

Maximum temperature: ……………………………………………………………………Suhu maksimum :…………………………………………………………………….

Temperature changes: ……………………………………………………………………...Perubahan suhu : ………………………………………………………………………[ 3 marks ]

(c) Calculate the heat released in this experiment.Hitungkan haba yang dibebaskan dalam eksperimen ini.

(specific heat capacity of water, c = 4.2 Jg-1oC , density of water = 1 gcm-3)( Muatan haba tentu larutan = 4.2 Jg-1°C, Ketumpatan larutan = 1 gcm-3 )

[ 3 marks ]

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2(c)

2(b)

2(a)

(d) Give an inference for this reaction.Berikan inferens bagi tindak balas ini.

…………..…………………………………………………………………………………………..

………….…………………………………………………………………………………………...

………….……………………………………………………………………………[ 3 marks ]

(e) In another experiment, excess zinc powder is added into 50 cm3 of 1.0 mol dm-3 copper(II)sulphate solution. Predict the change in temperature in this reaction. Dalam satu eksperimen lain, serbuk zink berlebihan ditambah ke dalam 50 cm3 larutan kuprum(II) sulfat 1.0 mol dm-3.Ramalkan perubahan suhu yang mungkin berlaku dalam tindak balas ini.

…………………………………………………………………………………………………..

[ 3 marks ]

(f) Write an ionic equation for the reaction in this experiment.Tulis persamaan ion bagi tindak balas yang berlaku dalam eksperimen ini.

………………………………………………………………………………………… [ 3 marks ]

set 7 p3

3

Plan an experiment to verify the above statement.Your planning should include the followings. Rancangkan satu eksperimen untuk mengesahkan pernyataan di atas. Perancangan anda hendaklah mengandungi perkara-perkara berikut:(a) Problem Statement

Pernyataan masalah (b) All the variables

Semua pemboleh ubah yang terlibat

(c) List of materials and apparatusSenarai bahan dan alat radas

(d) Procedure of the experiment

Prosedur eksperimen

(e) Tabulation of data Penjadualan data [17 marks]

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2(f)

2(e)

2(d)

Total

The value of heat of neutralisation for the reaction between hydrochloric acid and sodium hydroxide solution is higher than heat of neutralisation for the reaction between ethanoic acid and sodium hydroxide solution.Nilai haba peneutralan bagi tindak balas antara larutan asid hidroklorik dengan larutan natrium hidroksida lebih tinggi daripada haba peneutralan larutan asid etanoik dengan larutan natrium hidroksida

set 12 p32 Diagram 2 shows the apparatus set-up for an experiment to compare the heat of combustion of

methanol and ethanol. 200 cm3 of water is used in this experiment.Rajah di bawah menunjukkan susunan radas bagi eksperiment untuk membandingkanHaba pembakaran antara metano dengan etanol. 200 cm3 air digunakan dalam ekperimen ini.

Diagram 2Rajah 2

The table below shows the results obtained from the experiment I the heat of combustion of methanol and experiment II the heat of combustion of ethanol. Jadual di bawah menunjukkan keputusan eksperimen I haba pembakaran methanol dan eksperimen II haba pembakaran etanol.

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ThermometerThermometer

Tripod standTungku kaki tiga

Copper containerBekas kuprum

Spirit lamp Pelita

Wooden block Blok kayu

AlcoholAlkohol

WaterAir

Wind shieldPenghadang

ForExaminer’

s Use

Experiment IEksperimen I

Experiment IIEksperimen II

Initial temperature of water: …….................. Suhu awal air

Initial temperature of water: ......................... Suhu awal air

Highest temperature of water: ........................... Suhu tertinggi air

Highest temperature of water: .......................... Suhu tertinggi air

Initial mass of spirit lamp and methanol: .............gJisim awal pelita dan metanol

Initial mass of spirit lamp and ethanol: …....... gJisim awal pelita dan metanol

8

20

25

15

20

25

15

60

65

55

60

65

55

150.50245

151.35

Final mass of spirit lamp and methanol: ……......gJisim akhir pelita dan metanol

Final mass of spirit lamp and ethanol: ............. gJisim akhir pelita dan etanol

(a) Write the readings of the temperature and the mass of spirit lamp and alcohol in the spaces above.

Tuliskan bacaan suhu dan jisim pelita dan alkohol dalam ruangan di atas. [3 marks]

(b) Based on the information above, complete the table below.

9

150.50149.37

2(a)

ForExaminer’

s Use

Berdasarkan kepada maklumat di atas lengkapkan jadual di bawah.

Name of variablesNama pemboleh ubah

Action to be takenTindakan yang dibuat

(i) Manipulated variable: Pemboleh ubah dimanipulaskan:

………………..........……………………..

………………….........…………………..

(i) The way to manipulate variable: Cara mengubah pemboleh ubah dimanipulasi:

……………..................…………………………..

………….................……………………………...

(ii) Responding variable: Pemboleh ubah bergerak balas:

……………………………………………

……………………………………………

(ii) What to observe in the responding variable: Apa yang diperhatikan bagi menentukan pemboleh ubah gerak balas:

…………………..................……………………..

…………………..................……………………..

(iii) Fixed variable: Pemboleh ubah yang dimalarkan:

……………………………….…………..

……………………………………….…..

(iii) The way to maintain the controlled variable: Cara menetapkan pemboleh ubah dimalarkan :

……………………………………………………

……………………………………………………

[3 marks]

(c) (i) Calculate the energy change in the experiment I and II. Hitungkan perubahan tenaga dalam eksperimen I dan II

[Given: Energy change = mc, specific heat capacity of water, c = 4.2 Jg-1oC][Diberi: perubahan tenaga = mc, muatan haba tentu air, c = 4.2 Jg-1oC]

[3 marks]

(ii) Calculate the number of moles of methanol and ethanol burnt in this experiment.

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2(b)

2(c)(ii)

ForExaminer’

s Use

Hitungkan bilangan mol methanol dan etanol yang terbakar dalam eksperimen ini. [Molar mass of methanol = 32 g mol-1] [Molar mass of ethanol = 46 g mol-1] [Jisim molar metanol = 32 g mol-1] [Jisim molar etanol = 46 g mol-1]

[3 marks]

(iii) Calculate the heat of combustion of methanol in this experiment. Hitungkan haba pembakaran metanol dalam eksperimen ini.

[3 marks]

(d) Predict the heat of combustion of ethanol compare to the heat combustion of methanol. Ramalkan haba pembakaran etanol berbanding dengan haba pembakaran methanol.

………………………………………………………………………………………………………

………………………………………………………………………………………………………

[3 marks]

SET 13 (a) What is the meaning of heat of neutralisation?

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2(c)(ii)

2(c)(iii)

2(d)

Total

Apakah yang dimaksudkan dengan haba peneutralan?[ 1 mark ]

(b) Table 3.1 shows the heat of neutralisation for the reaction I, II and III using different acid reacted with sodium hydroxide solution.Jadual 3.1 menunjukkan haba peneutaralan bagi tindak balas I , II dan III menggunakan asid berlainan yang ditindak balaskan dengan larutan natrium hidroksida.

Reaction Tindak balas

Chemical EquationPersamaan kimia

Heat of neutralisationHaba peneutralan,

H(kJmol-1)I HCl + NaOHNaCl + H2O -57.0

II CH3COOH +NaOHCH3COONa +H2O -55.2

III H2SO4 + 2NaOHNa2SO4 + 2H2O xTABLE / JADUAL 3.1

(i) Explain why there is different in heat of neutralisation value in the reaction I and II.Terangkan mengapa terdapat perbezaan nilai haba peneutralan dalam tindak balas I dan II.

[ 3 marks ]

(ii) Reaction III has heat of neutralisation x kJmol-1. Predict the value of x and explain why. Tindak balas III mempunyai haba peneutralan sebanyak x kJmol-1.Ramalkannilai x dan terangkan mengapa .

[ 3 marks ](iii) You are given the following substance:

Sodium hydroxide 2.0 mol dm-3 , hydrochloric acid 2.0 mol dm-3 and ethanoic acid 2.0 mol dm-3 .Describe an experiment that can be done to compare the heat of neutralisation for the reaction I and reaction II. Your description should included table to record the result and steps of calculation involved.Anda dibekalkan dengan bahan berikut:Larutan natrium hidroksida 2.0 mol dm-3 , asid hidroklorik 2.0 mol dm-3 dan asid etanoik 2.0 mol dm-3.

Huraikan satu eksperimen yang dapat dijalankan untuk membandingkan haba peneutralan bagi tindak balas I dan tindak balas II.Huraian anda perlu mengandungi jadual bagi merekod keputusan dan langkah-langkah penghitungan yang terlibat.

[ 13 marks ]

SET 32 Table 2 shows the type of alcohol, molecular formula and heat of combustion.

Jadual 2 menunjukkan jenis-jenis alkohol, formula molekul dan haba pembakaran masing-masing.

Alcohol/Alkohol

Molecular formula/ Formula molekul

Heat of Combustion/Haba pembakaran

kJ mol -1

Metanol CH3OH -725

Etanol C2H5OH - 1 376

Propan-1-ol C3H7OH - 2 015

JADUAL 2

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(a) (i) What is meant by heat of combustionApakah yang dimaksudkan dengan haba pembakaran?

(ii) Explain why there is difference of the value of heat of combustion between three types of alcohol above.Terangkan mengapa terdapat perbezaan nilai haba pembakaran antara ketiga-tiga jenis alkohol di atas.

(iii) Between the three types of alcohol, which was the most suitable use as fuel. Explain why.Antara ketiga-tiga jenis alkohol di atas, yang manakah paling sesuai digunakan sebagai bahan api. Terangkan. [5 markah]

(b) You are given with buthan-1-ol. Using the suitable apparatus, explain an experiment to determine

heat of combustion of the alcohol. Your explanation have to consist of precautions taken and the calculation step.Anda dibekalkan dengan butan-1-ol. Dengan menggunakan radas yang sesuai, huraikan satu eksperimen bagi menentukan haba pembakaran alkohol tersebut.Huraian anda perlu mengandungi langkah berjaga-jaga dan langkah-langkah perhitungan yang terlibat. [11 markah]

(c) In one experiment to determine heat of precipitate of lead(II) sulphate, 50 cm3 of lead(II) nitrate 2.0 mol dm-3 and 50 cm3 sodium sulphate 2.0 mol dm-3 is added. The increasing of temperature is 10oC Dalam satu eksperimen bagi menentukan haba pemendakan plumbum(II) sulfat, sejumlah 50 cm3 larutan plumbum(II) nitrat 2.0 mol dm-3 di campur dengan 50 cm3 larutan natrium sulfat 2.0 mol dm-3. Kenaikan suhu campuran ialah 10oC.Chemical equation shows below:Persamaan tindak balas tersebut adalah seperti berikut:

Pb(NO3)2 + Na2SO4 PbSO4 + 2NaNO3

Calculated heat of precipitate of lead(II) sulphate in experiment.Hitungkan haba pemendakan plumbum(II) sulfat dalam eksperimen ini.[Gunakan maklumat muatan haba tentu larutan 4.2 J g -1 oC-1 ] [4 markah]

set 1210 Table 10 shows the molecular formula and heat of combustion of three types of alcohol.

Jadual 10 menunjukkan formula molekul dan haba pembakaran bagi tiga jenis alkohol.

Alcohol/Alkohol

Molecular formula /Formula molekul

Haba pembakaran /Heat of combustion

(kJ mol -1)

Methanol CH3OH 725

Ethanol C2H5OH 1 376

Propan-1-ol C3H7OH 2 015

TABLE / JADUAL 10

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(a) (i) What is the meaning of the ‘heat of combustion of an alcohol’?Apakah yang dimaksudkan dengan ‘haba pembakaran alkohol’?

[ 1 mark]

(ii) Explain why there are differences in the value of heat of combustion of the alcohols in Table 10. Terangkan mengapa terdapat perbezaan nilai haba pembakaran bagi alkohol-alkohol dalam Jadual 10.

[ 3 marks]

(c) Describe an experiment that you can carry out in your school laboratory to determine the heat of combustion of one of the alcohol in Table 10. Your description should include precautionary steps and the steps involved in the calculation.Huraikan satu eksperimen yang anda boleh jalankan di makmal sekolah anda bagi menentukan haba pembakaran salah satu alkohol dalam Jadual 10.

Huraian anda perlu mengandungi langkah berjaga-jaga dan langkah-langkah perhitungan yang terlibat. [12 marks]

(d) In another experiment to determine the heat of precipitation of lead (II) sulphate, 50.0 cm3 of 2.0 mol dm-3 lead(II) nitrate solution is reacted with 50.0 cm3 of 2.0 mol dm-3 sodium sulphate solution. Increment of the temperature in the mixture is 10 oC.Dalam satu eksperimen lain bagi menentukan haba pemendakan plumbum(II) sulfat, sejumlah 50 cm3 larutan plumbum(II) nitrat 2.0 mol dm-3 dicampur dengan 50 cm3 larutan natrium sulfat 2.0 mol dm-3. Kenaikan suhu campuran ialah 10 oC.

The equation for the reaction is :Persamaan bagi tindak balas tersebut adalah :

Pb(NO3)2 + Na2SO4 PbSO4 + 2NaNO3

Calculate the value of the heat of precipitation of lead(II) sulphate in this reaction.Hitungkan haba pemendakan plumbum(II) sulfat dalam eksperimen ini.

[Use the information that the specific heat capacity of water is 4.2 J g -1 oC-1 ][Gunakan maklumat muatan haba tentu larutan adalah 4.2 J g -1 oC-1 ]

[4 marks]

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