esei c6 2014

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SET 2 : ELECTROCHEMISTRY

(SECTION B)

5. (a) Table 5.1 show the results of series of experiments carried out to construct theElectrochemical Series. The positive terminal and value for the potential difference for the

pair of metals S and copper, Cu is not given. Q, R and S are not actual symbols of the metals.Jadual 5.1 menunjukkan keputusan satu siri eksperimen yang dijalankan untuk membina SiriElektrokimia. Terminal positif dan nilai beza keupayaan bagi pasangan logam P dan kuprum,Cu tidak diberi, Q, R dan S bukan simbol sebenar logam-logam itu.

Pair of metalsPasangan logam

Positive terminalTerminal positif

Potential difference(V)Beza keupayaan, (V)

Q , Cu Cu 2.7R , S S 0.5Q , R R 1.5

S , CuTable 5.1/Jadual 5.1

(i) Based on the values of the potential differences, arrange the metals in descending order

in the Electrochemical Series.Berdasarkan nila beza keuayaan, susun logam-logam tersebut dalam tertib

menurun dalam Siri Elektrokimia.[1 mark]

(ii) Predict the positive terminal and potential difference for the pair of metal S and metalCu.

Explain your answer.Ramalkan nilai terminal positif dan beza keupayaan bagi pasangan logam Sdan Cu.

[3 marks]

(b) Diagram 5.1 shows a voltaic cell. Metal P is situated above copper in the electrochemical

series.Rajah 5.1menunjukkan suatu sel kimia. Logam P terletak di atas kuprum dalam sirielekrokimia.

Diagram 5.1/Rajah 5.1

(i) State the positive terminal and the negative terminal of this cell.Nyatakan terminal positif dan terminal negatif bagi sel ini.

Solution Q

Larutan Q

Copper Metal P

Logam P

Copper(II) sulphate

Kuprum(II) sulfat

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(ii) Suggest a metal that is suitable as metal P and a solution that is suitable as solution Q.Cadangkan logam yang sesuai sebagai logam P dan larutan yang sesuai sebagai logam

P dan laturan yang sesuai sebagai larutan Q.[4 Marks]

(c) Diagram 5.2 shows the apparatus set-up to investigate an electrolysis process of an aqueous

potassium chloride using carbon electrodes.Rajah 5.2 menunjukkan susunan radas untuk menyiasat proses elektrolisis larutan kaliumklorida menggunakan elektrod-elektrodkarbon.


(i) State the observation at anode and cathodeNyatakan pemerhatian di anode dan di katod.

[2 marks](ii) Name of gas X and gas Y.

Namakan gas X dan gas Y[2 marks]

(iii) Explain your answer in terms of selective discharged of ion.Write the half-equations at the anode and cathode.Terangkan jawapan anda berdasarkan pemilihan discas ion.Tulis persamaan setengah di anod dan di katod.

[8 marks]

6. Diagram 6.1 shows the apparatus set-up to investigate the electrical conductivity of substances Sand R.Rajah 6.1 menunjukkan susunan radas untuk mengkaji kekonduksian elektrik bahan Sdan R.

Gas X Gas Y

Carbon electrodesElektrod karbon Potassium chloride solutionLarutan kalium klorida

A

Carbonelectrode

Elektrod karbonSubstance SBahan S

Substance R

Bahan R

Bulb does not light upMentol tidak menyalaBulb light upMentol menyala

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(a) Based on the observations in diagram 6.1

Berdasarkan pemerhatian dalam diagram 6.1.

(i) Give example of substance S and R.

Beri contoh bagi bahan Samd R[2 marks]

(ii) Explain the observationsTerangkan pemerhatian di atas.

[3 marks]

(b) Diagram 6.2 shows the apparatus set-up for chemical cell.

Rajah 6.2 menunjukkan susunan radas untuk satu sel kimia.


Based on diagram 6.2Berdasarkan rajah 6.2

(i) Identify positive and negative terminal of the chemical cellKenal pasti terminal positif dan terminal negatif bagi sel kimia.

[2 marks]

(ii) State the observation and half equation at zinc electrode.Nyatakan pemerhatian dan persamaan setengah pada elektrod zink.

[2 marks]

(iii) If zinc electrode is replaced with iron electrode, what will happen to the potentialdifference of the cell? Explain why.Jika elektrod zink digantikan dengan elektrod ferum, apakah akan berlaku pada

bacaan

beza upaya sel tersebut. Terangkan mengapa.[2 marks]

(c) Diagram 6.3 shows the arrangement of particles of a compound in two different states, Adan B.

Rajah 6.3 menunjukkan susunan zarah-zarah satu sebatian dalam dua keadaan yangberbeza,

Adan B.

V

Zinc electrode

Elektrod zinkCopper electrode

Elektronkuprum

Dilute sulphuric acid

Asid sulfurik cair

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State A State B

Keadaan A Keadaan B


(i) The compound can conduct electricity in state B but cannot do so in state A.Name one example of a compound with this property.

Sebatian ini boleh mengalirkan arus elektrik dalam keadaan B dan tidak bolehmengalirkan arus elektrik dalam keadaan A.

[1 mark]

(ii) Explain an experiment for the electrolysis of the compound you named in (c)(i).Your explanation must include the following:Terangkan satu eksperimen bagi elektrolisis sebatian yang anda namakan di(c)(i).

Penerangan anda haruslah merangkumi yang berikut:

A labeled diagram showing the apparatus set-upRajah berlabel yang menunjukkan susunan radas

The observation at the anode and cathodePemerhatian di anod dan di katod

Half equations at both electrodes

Setengah perasmaan bagi tindak balas di anod dan di katod

Products at the anode and cathade

Hasil di anod dan di katod[8 marks]

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SET 2 : ELECTROCHEMISTRY

(SECTION C)

7. (a) A student intends to electroplate iron spoon with silver metal.Suggest a suitable electrolyte and write the half-equations at the anode and cathode.

Draw a labeled diagram to show the apparatus set-upSeorang pelajar bercadang untuk menyadur sudu besi dengan logam argentum.Cadangkan electrolit yang sesuai dan tuliskan persamaan setengah di anod dan di katod.

[5 marks]

(b) Table 7.1 shows the result of experiment, set I and set II, to study the effect of metal Xand metal Y

on displacement of copper.Jadual 7.1 menunjukkan kuputusan eksperimen, Set I dan Set II bagi mengkaji kesan

logam X dan

logam Y ke atas penyesaran kuprum.

Experimenteksperimen

Apparatus set-upSusunan radas

ObservationPemerhatian

Set I Brown solid depositedPepejal perang dienapkanMetal X dissolvedLogam XmelarutThe blue color of solution fadesWarna biru larutan semakinpudar

Set II No changeTiada perubahan

Table 7.1/Jadual 7.1

Based on Table 7.1, explain the difference in observation in Set I and II.

[4 marks]

(c) Diagram 7.2 shows the order P, Q, R and S in the Electrochemical Series.Rajah 7.2menunjukkan susunan logam-logam P,Q,R dan S dalam Siri Elektrokimia.


P Q R S

Increasing order of electropositivitySusunan menaik keelektropositifan

Copper(II) sulphatesolutionLarutam kuprum(II)

sulfat

Metal X

Logam X

Copper(II) sulphate solutionLarutan kuprum(II) sulfat

Metal YLogam Y

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Describe an experiment to show the order of these metals in the Electrochemical Series.

Your description must include all the apparatus and material used observation and

conclusion.

Huraikan satu eksperimen untuk menunjukkan susunan logam-logam ini dalam SiriElektrokimia. Huraian anda mesti mengandungi semua alat radas dan bahan kimia yang

digunakan, pemerhatian dan kesimpulan.[10 marks]

ELECTROCHEMISTRY

Question

NoMak scheme Mark

1(a) Electrical to chemical energy / Tenaga elektrik kepada tenaga kimia 1(b) Pure copper /Kuprum tulen 1(c) Cu +and H+

1

(d)(i)(ii)

Become thicker / brown solid formedBertambah tebal / pepejal perang terbentukCu

2++ 2e Cu

11

(e) Blue solution remain unchanged // the intensity of blue solution is the same.Larutan biru tidak berubah // keamatan warna biru larutan adalah sama.

(i) the concentration of Cu2+ions remains the same.kepekatan ion kuprum(II) tidak berubah

(ii) the rate of ionized copper at the anode same as the rate of discharged

copper(II) ion at the cathode .kadar pengionan kuprum di anode sama dengan kadar ion kuprum(II)dinyahcaskan di katod

1

1

1

(f) Oxidation /pengoksidaanCopper atom released electron to form copper(II) ion.Atom kuprum mendermakan / membebaskan elektron menghasilkan ionkuprum(II).

11

(g) Electroplating of metal // extraction of metalPenyaduran logam // pengekstrakan logam

1

Total 11

QuestionNo

Mak scheme Mark

2(a)(i) Chloride ion / Cl-, hydroxide ion / OH-, sodium ion / Na+and hydrogen ion / H+

Ion klorida / Cl-, ion hidroksida /OH

-, ion natrium , Na

+dan ion hidrogen / H

+1

(ii) Cl-. The concentration of chloride ion is higher than hydroxide ion.Cl-. Kepekatan ion klorida lebih tinggi daripada ion hidroksida

1 + 1

(iii) 2Cl- Cl2 + 2e 1

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(b)(i)

Functional1Label - 1

11

(ii) - place lighted splinter at the mouth of the test tube containing hydrogengas

- pop sound produced

- Letakkan kayu uji menyala ke dalam tabung uji berisi gas hydrogen- Bunyi pop terhasil

1

1

(iii) -

Sodium ion and hydrogen ions move to the cathode, hydrogen ion isselectively discharged

- hydrogen ion is lower than sodium ion in the Electrochemical Series.- Ion natrium dan ion hydrogen bergerak / tertarik ke katod, ion hidrogen

terpilih untuk nyahcas / discas

- Ion hidrogen terletak di bawah ion natrium dalam Siri Elektrokimia

11

Total 11

Question

No

Mak scheme Mark

3(a) Cu + , H+

1(b) Carbon electrode which connect to copper electrode in cell A.

Because oxidation takes place

Elektrod karbon yang disambung kepada elektrod kuprum dalam sell AKerana proses pengoksidaan berlaku

11

(c)(i) Xsilver electrode / elektrod argentumYimpure silver electrode / elektrod argentum tak tulen

11

(ii) Ag+ + e Ag 1(d)(i) - The electrode become thinner

- Silver atom ionized / silver atom oxidized to form silver ion- elektrod semakin nipis

- atom argentum mengion / atom argentum dioksidakan membentuk argentumion.

11

(ii) Y : Ag Ag+ + eZ : Ag

++ e Ag

11

(e) The waste chemicals emitted contain poisonous heavy metal ions and cyanideions / alter the pH of water.Bahan buangan kimia dibebaskan mengandungi logam berat yang beracun dansianid / mengubah nilai pH air

1

11

QuestionNo

Mak scheme Mark

Carbon electrodesElektrod karbon

Sodium sulphate

solutionLarutan natrium

sulfatA

Oxygen gas

Gas oksigen

Hydrogen gas

Gas hidrogen

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4(a)(i) Lead(II) ion// Pb +, bromide ion// Br-

Ionplumbum(II)// Pb2+, ion bromida// Br-1

(ii) Sodium ion // Na+, hydrogen ion// H+, sulphate ion// SO4-, hydroxide ion//OH-

ion natrium // Na+, ion hidrogen// H

+, ion sulfat // SO4

2-, ion hidroksida //OH

-1

(b)(i) Lead /Plumbum 1

(ii) Pb2+ + 2e Pb 1

(iii) Brown gas / Gas berwarna perang 1

(c)(i) hydroxide ion / ion hidroksida 1

(ii) Anode : Oxygen gasanod : Gas oksigenCathode : hydrogen gasKatod : gas hidrogen

1

1

(iii) Sodium nitrate solution // sulphuric acidLarutan natrium nitrat // asid sulfurik(Any suitable electrolyte) 1

9

Rubric Mark

5(a) (i) Q, R, S , Cu 1. 1

(ii) positive terminal : CuPotential difference : 0.7 VS is higher than Cu in the Electrochemical Series

111

..... 3(b) (i) positive terminal : copper / CuNegative terminal : Metal P

(ii) metal P : Zinc / Zn // Magnesium/Mg

(any suitable metal)Solution Q : Zinc sulphate // magnesium sulphate(any suitable electrolyte)

111

1

..... 4

(c) (i) anode : greenish yellow gascathode : colourless gas (bubbles)

11.. 2

(ii) gas X : hydrogengas Y : chlorine 11.. 2

(iii)

Anode Cathode

Ions move to / ionattracted to

Hydroxide ion/OH-

Chloride ion/Cl-

Hydrogen ion/H+,

Potassium ion/K+

Ions selectivelydischarged Cl

-

H

+

1+1

1+1

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Reason Concentration Cl-higherthan OH

-Position of hydrogenion/H

+is lower than

potassium ion/K+in theElectrochemical Series.

Half equation 2Cl- Cl2 + 2e 2H

+ + 2e H2

1+1

1+1

. 8

Total 20

Question

NoMak scheme Mark

6(a) (i) Substance S : Glucose / ethanol (any suitable covalent compound)Substance R : Sodium chloride solution ( any salt solution / acid / alkali)

11

.. 2

(ii) 1. S conducts electricity but R does not

2. S has free moving ions // ions free to move3. R consists of molecules / no free moving ions

111

.. 3

(b) (i) negative terminal : zincpositive terminal : copper

11

.. 2(ii) 1. zinc electrode become thinner

2. Zn Zn2+

+ 2e11

.. 2(iii) 1. the potential difference decreases

2. iron is lower than zinc in the Electrochemical Series //iron is less electropositive than zinc // distance between iron and

copper is shorter than distance between zinc and copper in theElectrochemical Series

1

1

.. 2(c) (i) Sample answer

Lead(II) bromide / lead(II) iodide /sodium chloride/sodium iodide(any suitable ionic compound)r : substance that decompose when heated.

Example : lead(II) nitrate, lead(II) carbonate

1

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(ii)

Diagram:FunctionalLabel

Observation:Anode : brown gas

Cathode: grey solid

Half equation:Anode : 2Br

- Br2 + 2e

Cathode : Pb2+

+ 2e Pb

Product:Anode : leadCathode : bromine gas

11

11

11

11

.. 8

Total 20

Question

NoMak scheme Mark

7(a) Sample answerSilver nitrate solution

Functional1Label - 1

Anode : Ag Ag++ e

Cathode : Ag+ + e Ag

1

11

11.. 5

(b) 1. metal X is more electropositive than copper // X is higher than copper in theElectrochemical Series

2. atom X oxidises to X ion // atom X releases electron

3. copper(II) ion accepts electron to form copper4. the concentration of copper(II) ion decreases

1111

Carbon electrodes

Elektrod karbon

PbI2// PbBr2//

NaCl

Heat

Panaskan

Note :

Observations and half-equationsare based on the substance

suggested.

Silver nitrate solutionIron spoon

Silver

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5. metal Y is less electropositive than copper // Y is lower than copper in theElectrochemical Series

1.. 5

(c) Material0.5 mol dm

-3of P nitrate, Q nitrate, R nitrate, S nitrate solutions, metal P, Q, R

and S

ApparatusTest tube, test tube rack, sand paper

Procedure1. Clean the metal strips with sand paper2. Pour 5 cm3of P nitrate solution , R nitrate solution , S nitrate solution into

different test tubes.

3. Place a strip of metal P into each test tube4. Record the observation after 5 minutes5. Repeat steps 2 to 4 using strip of metal Q, R to replace metal P.

Observation

Metal Metal ion P Metal ion Q Metal ion R Metal ion SP X X X

Q / X X

R / / X

S / / /

1

1

11

111

11

ConclusionThe electropositivity of metals increases in the order of P,Q,R,S 1

..10TOTAL 20

esei c6 2014

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