Kimia P2 Sbp Mid Year Spm 2008

Nama: ....................................................

Tingkatan: ..............................

SULIT 4541/2 Chemistry Paper 2 MEI 2008 2 ½ jam BAHAGIAN SEKOLAH KEMENTERIAN PELAJARAN MALAYSIA PEPERIKSAAN PERTENGAHAN TAHUN 2008 FORM 5 CHEMISTRY Paper 2 Dua jam tiga puluh minit JANGAN BUKA KERTAS SOALAN INI SEHINGGA DIBERITAHU

1. 2.

3.

4.

5.

6.

Tuliskan nama dan tingkatan pada ruang yang disediakan. Jawab semua soalan daripada Bahagian A. Tuliskan jawapan anda dalam ruang yang disediakan Jawab satu soalan daripada Bahagian B dan satu soalan daripada Bahagian C.Jawapan kepada bahagian B dan Bahagian C hendaklah ditulis pada kertas tulis. Anda diminta menjawab dengan lebih terperinci untuk Bahagian B dan Bahagian C. Jawapan mestilah jelas dan logik. Persamaan, gambar rajah, jadual, graf dan cara lain yang sesuai untuk menjelaskan jawapan anda boleh digunakan. Anda hendaklah menyerahkan kertas tulis dan kertas tambahan, jika digunakan bersama-sama dengan kertas soalan. Penggunaan kalkulator saintifik yang tidak boleh diprogramkan adalah dibenarkan.

Bahagian

A

B

C

Soalan

1 2 3 4 5 6 7 8 9 10

Markah penuh

Markah diperoleh

10 10 10 10 10 10 20 20 20 20 Jumlah

Kertas soalan ini mengandungi 17 halaman bercetak [lihat sebelah SULIT

SULIT 1.

Figure 1 shows the location of seven elements A, D, E, G, J, L and M in the Periodic Table. These are not the actual symbols of the elements. 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18

A

D

E

G J

L

Diagram 1 Using the letters in the Periodic Table of the elements in the Diagram 1, answer the following questions. (a)

(i)

Which of the element is chemically unreactive?

(ii)

……………………………………………………………………………… [1 mark] Give one reason for your answer in a(i). ……………………………………………………………………………… [1 mark]

(b)

When a small piece of element A is put into water, alkaline solution is formed and hydrogen gas is released. (i)

Write the chemical equation for the above statement. ……………………………………………………………………………… [1 mark]

(ii)

State one precaution that must be taken while carrying out the experiment using element A. ……………………………………………………………………………….. [1 mark]

(c)

Arrange A, D, E, G, J and L according to the increase in size of the atom. ……………………………………………………………………………………… [1 mark]

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SULIT

SULIT (d)

Why are elements A and L placed in the same group?

(e)

……………………………………………………………………………………… [1 mark] Element D reacts with element E to form a compound. (i)

Write the chemical formula of this compound. ……………………………………………………………………………… [1 mark]

(ii)

Draw the diagram of electron arrangement for the compound that is formed between D and E.

[2 marks] (iii)

Why the compound in d (ii) cannot conduct electricity in any state. ……………………………………………………………………………. [1 mark]

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SULIT

SULIT 2.

Graph 2.1 shows the temperature against time when solid naphthalene is heated. 0

Temperature / C

S

Q

T1

R

T0 P

Time/s

Graph 2.1

(a)

State the melting point of naphthalene. ........................................................................................................................ [ 1 mark]

(b)

What is the physical state of naphthalene at: (i)

PQ ........................................................................................................................

(ii)

RS ........................................................................................................................ [ 2 marks]

(c)

Explain why there is no change in temperature from Q to R. .............................................................................................................................. .............................................................................................................................. [ 2 marks]

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SULIT

SULIT (d)

State how the movement of naphthalene particles changes between R and S during heating. ………………………………………………………………………………............ [ 1 mark]

(e)

Table 2.2 shows four substances and their respective formulae.

Substances

Chemical formula

Iodin Copper Naphthalene Copper(II) sulphate

I2 Cu C10H8 CuSO4 Table 2.2

Use information from table 2.2 to answer the following questions. (i)

State one substance which exist as a molecule. ....................................................................................................................... [ 1 mark]

(ii)

Which substance can conduct electricity in the solid state?

(iii)

........................................................................................................................ [ 1 mark] What type of particle presents in copper(II) sulphate? ........................................................................................................................ [ 1 mark]

(f)

A few drops of liquid bromine are dropped into a gas jar. The brown bromine vapour spreads to the upper part of the gas jar. The time taken is very short. Name the process occurs. ……………………………………………………………………………................ [ 1 mark]

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SULIT

SULIT 3.

Diagram 3 shows a flow chart for the industrial manufacture of compound Z from sulphuric acid and ammonia.

Contact Process

Sulphuric acid

Reaction X Compound Z Haber Process

Ammonia

Diagram 3 (a)

(i)

Ammonia is produced during Haber process. Write the chemical equation for the formation of ammonia. ……………………..……………………………………………................ [1 mark]

(ii)

What is the source of nitrogen used? ……………………..…………………………………………………….... [1 mark]

(b)

In the above diagram, sulphuric acid reacts with aqueous ammonia to form compound Z. (i)

Name the reaction X. ...................………………………………………………………................. [1 mark]

(ii)

Write the chemical equation for reaction X. …………………………………………………………………………….... [1 mark]

(iii)

What is the use of compound Z in daily life? ………………………………………………………………………............ [1 mark]

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SULIT

SULIT (c)

 Bronze and pewter are two example of an alloy.  Bronze is made up of copper as a major component and other elements.  Bronze is harder than pure copper.

(i)

Name the element added to copper to form bronze. ……………………………………………………………………………… [1 mark]

(ii)

Draw an arrangement of the particles in: pure copper

[1 mark] bronze

[1 mark] (iii)

Explain why bronze is harder than pure copper? ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ [2 marks]

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SULIT

SULIT 4.

A student carried out an experiment to investigate the purification of impure copper rods.

(a)

Draw a labelled diagram to show the apparatus set- up of to carry out this experiment.

[3 marks]

(b)

The experiment was conducted for 30 minutes. (i)

What would be observed at the electrodes? Anode: ........................................................................................................................ Cathode: ....................................................................................................................... [2 marks]

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SULIT

SULIT (ii)

What happened to the concentration of the electrolyte? Explain. ........................................................................................................................ ....................................................................................................................... ....................................................................................................................... [2 marks]

(c)

Write the half equation for the reaction at the anode and the cathode. i)

Anode: ........................................................................................................................

ii)

Cathode: ........................................................................................................................ [2 marks]

(d)

State another application of electrolysis. ……………………………………………………………………………………… [1 mark]

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SULIT 5.

Table 5 shows the data of two experiments that have been carried out to determine the rate of decomposition of hydrogen peroxide to water and oxygen gas by using manganase (IV) oxide as a catalyst.

Experiment

Volume of

Concentration of

hydrogen peroxide /cm3

peroxide /mol dm-3

I

20

2

II

20

4

hydrogen

Table 5

(a)

Write the chemical equation for decomposition of hydrogen peroxide. …………………………………………………………………………………........ [1 mark]

(b)

Calculate the volume of oxygen gas released in experiment I at room condition.

( 1 mole of gas occupies 24 dm3 at room condition )

[3 marks] (c)

(i)

Compare the rate of decomposition of hydrogen peroxide between experiment I and II. …………………………………………………………………………….... [1 mark]

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SULIT

SULIT (ii)

Based on collision theory, explain your answer in (c) (i). ……………………………………………………………………………… …………………………................................................................................ ……………………………………………………………………………… …………………………................................................................................ [3 marks]

(d)

Sketch the graph of volume oxygen gas against time for experiment I and experiment II by using the same axis.

[2 marks]

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SULIT

SULIT 6.

Figure 6 shows the conversions of organic compound A to another substances, C2H4(OH)2 and C2H5OH through Processes A and C.

Reagent B

C2H4(OH)2

Process A Compound A

Process C

C2H5OH

Steam Diagram 6 (a)

What is meant by organic compound? ………………………………………………………………………………............ ………………………………………………………………………………............ [1 mark]

(b)

(i)

Write the molecular formula of compound A.

(ii)

………………………………………………………………………............ [1 mark] Name the compound A. ………………………………………………………………………............ [1 mark]

(iii)

Identify a functional group of compound A. ………………………………………………………………………............ [1 mark]

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SULIT

SULIT (c)

Compound A reacts with Reagent B to produce substance C2H4(OH)2 through Process A. (i)

Suggest Reagent B. ……………………………………………………………………................ [1 mark]

(ii)

Name Process A. ………………………………………………………………………............ [1 mark]

(iii)

State the observation when the reaction occurs. ………………………………………………………………………............ [1 mark]

(d)

Substance C2H5OH is produced when the compound A reacts with steam through Process C. (i)

Write the equation to show the reaction. ………………………………………………………………………............ [1 mark]

(ii)

State the homologous series represented by C2H5OH. ………………………………………………………………………............ [1 mark]

(iii)

State one condition that must be used to carry out Process C. ………………………………………………………………………............ [1 mark]

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SULIT

SULIT Section B ( 20 marks ) Answer any one question from this section. The suggested time to answer section B is 30 minutes.

7.

Diagram 7 shows the chemical symbols which represent three elements X, Y and Z These letters are not the actual symbols of the elements. 23

35

X

12

Y

11

17

Z 6

Diagram 7

(a)

What is meant by: i)

Ionic compound

ii)

Covalent compound [2 marks]

(b)

Explain the formation of the bond that is formed between i) ii)

element X and element Y. element Y and element Z. [12 marks]

(c)

The melting point of magnesium oxide is much higher than methylbenzene. Explain why. [6 marks]

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SULIT

SULIT 8. (a) What are meant by empirical formula and molecular formula. [2 marks]

b)

A carbon compound has an empirical formula of CH2 and a molar mass is 70 g mol-1, determine its molecular formula. [Relative atomic mass : H=1 , C=12] [3 marks]

(c)

(i)

Metal Z reactively react with oxygen to form Z oxide. Describe the prosedure to determine the empirical formula of Z oxide. The procedure should included a precaution. [10 marks]

(ii)

Diagram 8 shows the result obtain in c(i).

Mass of crucible + lid, g Mass of crucible + lid + Z, g Mass of crucible + lid + Z oxide, g

= = =

46.30 46.30 46.62

Diagram 8

Based on the information in Table 8, determine the values of the following : [Relative atomic mass : O=16 , Z=65]

i) ii) iii) iv) v)

mass of lead number of moles of lead mass of oxygen number of moles of oxygen empirical formula of lead oxide [5 marks]

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SULIT

SULIT Section C ( 20 marks ) Answer any one question from this section. The suggested time to answer section C is 30 minutes.

9.(a)

Write two balanced chemical equation to show the chemical properties of an acid. [2 marks] Diagram 9 shows the structural formula of methanoic acid.

O H

C

O

H

Diagram 9

(b)

(i)

Explain why methanoic acid is a weak acid. [2 marks]

(ii)

Glacial methanoic acid does not conduct electricity but the aqueous methanoic acid does. Explain. [3 marks]

(c)

You are required to prepare a dry zinc(II) sulphate using 100 cm3 sulphuric acid 0.1 mol dm-3.

(i)

Describe the laboratory experiment to prepare the dry of zinc(II) sulphate [7 marks]

(ii)

Calculate the mass of dry zinc sulphate formed. [Relative atomic mass: H=1, O=16, S=32, Zn=65] [4 marks]

(d)

Give two examples of salt and the uses in daily life. [2 marks]

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SULIT

SULIT 10.

Diagram 10.1 shows how compound M is formed from ethanoic acid and propanol. ethanoic acid + propanol Concentrated H2SO4

Compound M

Diagram 10.1

(a)

Based on the information given, (i)

what is the role of concentrated sulphuric acid, H2SO4 in this reaction.

(ii)

name the reaction for the preparation of compound M.

(iii)

write the chemical equation for the reaction of propanoic acid with ethanol

(iv)

draw structural formula and give name for compound M.

(v)

state two special characteristics for compound M.

(vi)

draw the structures of the two isomers of propanol. [10 marks]

(b)

Table 10.2 shows the results of latex coagulation. Procedure

Observations

Latex is left under natural condition Ammonia solution is added to latex

Latex coagulates Latex does not coagulate

Table 10.2 (i)

Explain why there is a difference in this observation. [6 marks]

(ii)

Explain how vulcanization of rubber can improve the weakness of natural rubber. [4 marks] END OF QUESTION PAPER

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SULIT

SULIT 4541 Chemistry Marking Scheme Mei 2008

4541/1/2/3

BAHAGIAN SEKOLAH KEMENTERIAN PELAJARAN MALAYSIA ______________________________________________ PEPERIKSAAN PERTENGAHAN TAHUN 2008

FORM 5 CHEMISTRY MARKING SCHEME FOR PAPER 1, 2 AND PAPER 3

Peraturan pemarkahan ini mengandungi halaman bercetak.

1

PAPER 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

B C B C D A B A D D D C A A C B C C C C

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

2

D D B A C A D A C A A B D A C A D B B D

41 42 43 44 45 46 47 48 49 50

D B D C B A B D C B

PAPER 2-SECTION A No. 1

Rubric a

Mark

G

1

Has stable /octet electron arrangement//8 valence electron

1

2A + 2H2O  2AOH + H2

1

Use a small pieces//use a forcep// use a google

1

c

G,E,D, A,J,L

1

d

Has same valence electron// valence electron is 1

1

e (i)

DE2 r: E2D

1

b (i) (ii)

(ii)

[can draw the diagram of electron arrangement correctly] - Correct structure of atoms - Correct ratio of atoms=1:2

2

Has (neutral ) molecule

1

TOTAL

10

a

T1

1

b(i)

PQ: solid + liquid

1

RS: liquid

1

Heat energy absorbed

1

is used to overcome the forces of attraction between particles

1

(iii)

2

(ii) c

// Heat is absorbed to overcome the intermolecular forces r: ion/atom (1+1) d

The particles / molecules move faster

1

e (i)

Iodine/I2//napthalene/C10H8

1

(ii)

Copper/ Cu

1

(iii)

Ion

1

Diffusion

1

TOTAL

10

3

3

a (i)

3H2 + N2  2NH3

1

(ii)

( Extract from ) air

1

Neutralization

1

H2SO4+ 2NH3  (NH4)2SO4

1

b (i) (ii)

//H2SO4+ 2NH4OH  (NH4)2SO4 + H2O (iii) c (i)

Fertilizer

1

Tin

1

(ii)

Copper atom

Tin atom

Copper atom

(1+1) 

d

In pure copper the layer of atom are easily slide over each other when external force is applied on them.



1

The different size of foreign atoms in allloy are prevent the layers of atom from slide each other when external force is

1

applied.

4

a

TOTAL

10

1 Diagram of set up of apparatus complete and functional

1

2 Label (Anode) – impure copper and (cathode )– pure copper

1

3 ( Electrolyte) – copper (II) sulphate / copper (II) chloride // copper (II) nitrate solution

1

a: chemical formula

b(i)

(ii)

1 become thinner // decrease in mass

1

2 become thicker // increase in mass

1

1 ( Remain )unchanged

1

2 Number of Cu2+ ions produced at anode same as number of copper atoms produced at cathode // the rate of formation of Cu2+

4

ions at the anode is the same as the rate of discharge of Cu2+ at cathode.

c (i) (ii)

d

5

1

(Anode ):Cu  Cu2+ + 2e (Cathode ): Cu

2+

1

+ 2e  Cu

1

Electroplating of metals/ Extraction of reactive metals

1

TOTAL

10 

a

2H2O2

b

Number of mole of H2O2 = 20 x 2/1000= 0.04

O2 + 2H2O

1

1

2 mol of H2O2 produce 1 mol of O2 // Number of mole of O2 = 0.04/2 = 0.02

1

Volume, O2 = 0.2 x 24dm3 = 4.8 dm3 c (i) (ii)

1

Rate of reaction in experiment II is higher than experiment I 

The concentration/number of molecule per unit volumeof hydrogen peroxide in II is higher

d

1 1 1



The frequency of collision between H2O2 molecule is higher



The frequency of effective collision is higher

1

Volume of gas/cm3

II I

Time(s) Label Y axes and X axes Correct curve and label I and II

1 1

10

TOTAL

5

6

A compound that contain element of carbon and derive from living

a

1

organisms.

C2H4

1

(ii)

ethene

1

(iii)

double bond between carbon atoms

1

b (i)

(a: C=C ) c (i)

Acidified potassium manganat (VII) // Acidified potassium

1

dicromate (VI) (ii)

Oxidation

1

(iii)

Purple to colourless // orange to green

1

C2H4 + H2O  C2H5OH

1

(ii)

Alcohol

1

(iii)

Temperature 300 oC // Pressure 60 atmosphere // concentrated

d (i)

phosphoric acid

1

TOTAL

10

6

SECTION B No. 7

Rubric a (i)

Mark

Compound that form when non metal atom gain/receive/accept electron that release/lose/donate by metal atom to achieve stable /octet/duplet electron arrangemen

1

(ii) Compound that form between non metal atom by sharing their valence electron to achieve stable/octet /duplet electron

1

arrangement

b

Between P and Q  

Atom X has 1 valence electron

1 +

Atom X loses/donates/transfers 1 electrons to form X ion //

X X+ + e- and attain stable octet electron arrangement 

Atom Y has 7 valence electrons



Atom gains/receives/accept 1 electron to formY- ion//

1 1 1

Y + e-Y

attain the stable /octet electron arrangement



The two oppositely-charged ions// the X+

1

and Y- ion are

bonded together by a strong electrostatic force 

To form a ionic compound with the formula XY// diagramn

X Y

Max 7

7

1 1

(ii)

Between Y and Z 

Atom Z has 4 valence electrons and atom Y has 1 valence

1

electrons 

One atom Z contributes 4 electrons and (each) atom Y 1

contributes one electron for sharing . 

Atom Z shared 4 pairs of electron with 4 atoms Y



to attain a octet /stable electron arrangement respectively



diagram

1 1 1

Y

Z

Y

Y

Y

(iii) 

Magnesium oxide is an ionic compounds



Strong electrostatic force of attraction exists between

1

1

Mg2+ and O2 -// the oppositely-charged magnesium ions and oxide ions in Magnesium oxide are held together by strong ionic bonds 

A lot of heat energy // high of energy is required to break the strong forces

1



Tetrachloromethane is a covalent compound

1



Weak intermolecular forces //held together by weak (Van der

1

Waals) force of attractions between molecule 

little heat energy //low energy is needed to overcome the weak forces

8

1

8

a

TOTAL 20 Empirical formula- Formula shows simplest ratio of atoms of each 1 element in the compound Molecular formula- Formula shows actual number of atoms of each element in the compound

b

Molecular Formula = ( Empirical formula )n = ( CH2 )n Relative Molecular Mass ( CH2 )n = 70 12n + 2n= 70 14n=70 n=5 Molecular Formula C5H10

c(i)

1

1

1 1

1. Metal Z is cleaned using sand paper

1 2. A crucible and its lid are weighed and the mass is recoded 1 3. Metal Z is palced in the crucible. The crucible,lid and its content is weighed and the mass is recorded.

1

4. The crucible with its content is heated strongly without lid.

1

5. When metal Z start burn, the crucible is covered by its lid

1

6. the covered is raise a little at intervals

1

7. When there is no more reaction, the lid is removed and the crucible is heated strongly for a few minutes. 8. Cool the crucible and weigh the crucible,its lid and its

1 1

Content and record the mass. 9. The process of heating, cooling and weighing is repeated

1

until constant is obtained. 10. (Precaution step ); Close the crucible immediately to prevent loss of

9

1

Element

Z

O

Mass(g)

1.30

0.32

1

1 mol

1.30/65=0.02

0.32/16=0.02 1

Simplest ratio

1

1 1

Empirical Formula ZO

1

TOTAL

20

10

PAPER2 –SECTION C Rubric

No 9

Mark

Sample answer :

a

Zn + HNO3 

Zn(NO3)2 + H2O

ZnCO3 + HNO3  Zn(NO3)2 + H2O + CO2 ZnO + HNO3  Zn(NO3)2 + H2O

b (i)

(ii)

c(i)

Any two

2



Methanoic acid partial ionizes in water

1



produce low concentration of hydrogen ion

1



Glacial ethanoic acid has (neutral) molecule

1



Methanoic acid aqueous ionizes in water

1



to produce free moving ion

1

Procedure : 1 100 cm3 of 0.1 moldm-3 sulphuric acid is poured into a beaker

1

and heated slowly. 2 zinc carbonate is added into the sulphuric acid until in excess/no longer dissolves.

1

3 Stir the solution and filtered.

1

4 The filtrate is poured into an evaporating dish and heat until saturated

1

5 The hot saturated salt solution is allowed to cool 1 6 The crystals formed are filtered out, rinsed with distilled water 7 dried between sheets of filter paper.

11

1

(ii)

ZnCO3 + H2SO4  ZnSO4 + H2O + CO2

1

Number of mole , H2SO4 = 0.1( 100 )/1000 = 0.01

1

1 mol of H2SO4 produce 1 mol of ZnSO4 1

Mole of ZnSO4 = 0.01 Mass of ZnSO4 = 0.01 X 161 = 16.1 g Sample answer :

d

1 ammonium chloride as a fertilizer 2 copper (II) sulphate as a pesticide 3 hydrated calcium sulphate to make plaster casts 4 sodium chloride food additive Any 2 suitable anwers(1+1) TOTAL 10a

1

(i) (ii) (iii)

1 1

20

catalyst

1

esterification

1

CH3COOH + C3H7OH  CH3COOC3H7 + H2O

1

Correct reactant Correct product

1

(iv)

Ethyl propanoate Sweet smell/fruity smell/fragrant smell //insoluble in water/soluble in organic solvent //colourless //less dense than water

2

any two properties (1+1) (v)

2

12

 b

(i)

Bacteria will produce lactic acid/H+ ions which neutralize negatives charge of the protein membrane/ rubber molecules



The rubber molecules will be collide with each other and cause protein membrane broken



1 1

Rubber polymer are released and lump together 1



Hydroxide ions/OH- from ammonia solution will neutralise H+ produced by acid



The protein membrane remains negatively charged



The rubber particles repel each others/ the rubber polymers cannot combine and coagulate

(ii)



1 1

The presence of cross-linkage of sulphur atoms between the rubber molecule



1

1

When vulcanized rubber is stretched and release, the crosslinkage will pull the chain back to their original arrangement

1



Diagram



Improves the elasticity and strength of the rubber / make

1

vulcanized rubbers more resistant to heat /organic solvent 1

 or Resistant to oxidation : 

The presence of cross-linkage of sulphur atoms between the rubber molecule

1



Diagram



C=C in vulcanized rubber is less than C=C in the

1

unvulcanized rubber, 

1

so vulcanize rubber is more resistant to oxidation 1 TOTAL 20

13

PAPER 3 1 (a) KK0503 – Measuring and using numbers EXPLANATION [Able to write all the times with units accurately] Suggested answer:

SCORE 3

t1 55.0 s, t2 48.0 s , t3 42.0 s , t4 37.0 s , t5 33.0 s [Able to record all the times accurately but without units / no decimal place] t1 55.0 , t2 48.0 , t3 42.0 , t4 37.0 , t5 33.0 // // t1 55 s , t2 48.0 s , t3 42 s, t4 37s, t5 33s

2

[Able to write at least 3 readings of the times accurately]

1

No response given / wrong response

0

1 (b) KK0501- Observation EXPLANATION [Able to state the colour of sulphur and the rate of it is formed] Suggested answer:

SCORE 3

Pale / light yellow precipitate is slowly formed [Able to state the colour of sulphur] Pale / light yellow precipitate is formed. [Able to state the formation of precipitate] A precipitate is formed. No response given / wrong response

2 1 0

1 (c) KK0506 – Communicating EXPLANATION [Able to construct a table correctly containing three labeled columns with correct units and record all the time and 1/time accurately ]

SCORE

Suggested answer: Temperature, o C Time , s 1 / time , s-1

30

35

40

45

50

55.0 0.018

48.0 0.021

42.0 0.024

37.0 0.027

33.0 0.030

3

[Able to construct a table correctly containing three labeled columns with correct units and record all the time and 1/time but not accurately]

2

[Able to write at least 3 readings of the times accurately]

1

No response given / wrong response

0

1 (d) (i) KK0506 Communicating 14

EXPLANATION [Able to draw a graph accurately that consists of the following aspects] Suggested answer:

SCORE 3

1. Both axes labeled and units ( Y axis - temperature , X axis – 1/ time ) 2. All points transferred correctly 3. Uniform scale, graph size covers at least half of the graph paper. 4. Straight line/ best fits drawn [Able to draw a graph that consists of the following aspects] 1. Both axes labeled / units ( Y axis - temperature , X axis – 1/ time ) 2. At least three points transferred correctly 3. Uniform scale, graph size covers at least half of the graph paper. 4. Straight line/ best fits drawn

2

[Able to draw a graph that consists of the following aspects] 1. Both axes labeled and units ( Y axis - temperature , X axis – 1/ time ) 2. Draw a line

1

No response given / wrong response

0

1(d)(ii) KK0509 – To define Operationally EXPLANATION [Able to interpret the relationship between the rate of reaction and the temperature of sodium thiosulphate solution from graph accurately] Suggested answer: The rate of reaction is directly proportional to the temperature of sodium thiosulphate solution // As the temperature of sodium thiosulphate increases the rate of reaction increases. [Able to interpret the relationship between the rate of reaction and the temperature of sodium thiosulphate solution from graph ] The rate of reaction is proportional to the temperature // the temperature is proportional to the rate of reaction // the rate of reaction increases when the temperature increases. [Able to state an idea of hypothesis The temperature affects the rate of reaction. No response given / wrong response

SCORE 3

2

1

0

15

Temperature /oC

50

X

45

X

40

X

35

X

30 X 0.015

0.020

0.025

16

0.030

1/time , s-1

1(e) KK0510 - State variables EXPLANATION [Able to state three variables and three action to be taken] Suggested answer: Variable Manipulated: Temperature

Action to be taken Heat the sodium thiosulphate solution at different temperature // Use different temperature. Record the time taken for “X” mark to disappear from view.

SCORE

3

Responding: Rate of reaction / time taken for “X” marks to disappear from view. Controlled : Use the same concentration and Concentration and volume of H2SO4, volume of H2SO4 /sodium concentration and volume of sodium thiosulphate solution // Use same thiosulphate solution, size of conical size conical flask. flask. [Able to state any two variables and any two action to be taken]

2

[Able to state any one variables and any one action to be taken]

1

No response given / wrong response

0

2 (a) KK0506 Communicating EXPLAINATION [Able to write the correct overall ionic equation] Suggested answer: Mg + Cu2+  Mg2+ + Cu Mg + CuSO4  MgSO4 + Cu Mg  Mg2+ + 2e // Cu2+ + 2e  Cu No response given / wrong response

SCORE 3

2 1 0

2(a)(i) KK 0504 – Making inference EXPLANATION [Able to state the correct inference] Suggested answer: Magnesium atom releases/donate/loses electrons to produce magnesium ion // Magnesium is corrode. Magnesium becomes thinner // mass of magnesium decreases Magnesium dissolves No response given / wrong response

17

SCORE 3

2 1 0

2(b) KK 0505 - Predicting EXPLANATION [Able to state the voltage value] 0.65 V 0.63 – 0.64 V // 0.66 – 0.67 V < 0.64 V // > 0.67 V No response given / wrong response 2(c)KK 0508 – Interpreting Data EXPLANATION [Able to arrange the position of all metals in an ascending order based on tendency to release electrons correctly] Copper > Lead > Iron > Zinc > Magnesium

SCORE 3 2 1 0

SCORE 3

[Able to arrange the position of all metals in descending order based on tendency to release electrons] Magnesium > Zinc > Iron > Lead > copper

2

[Able to arrange the position of at least four metals in ascending order based on tendency to release electrons correctly]

1

No response given / wrong response

0

2(d) KK0509 – Operational definition EXPLANATION [Able to state the correct and complete operational definition] Suggested answer:

SCORE 3

The further the metal is from copper in the electrochemical series, the greater is their voltage reading. // [Able to give incomplete relationship] Suggested answer:

2

The further apart the metal is in the electrochemical series, the greater the potential difference / voltage reading. [Able to state an idea] Suggested answer:

1

The position of metal influence the voltage reading // Type of metal influence the voltage reading. No response given / wrong response

0

18

3.(a) KK051021 – Statement of problem EXPLANATION [Able to make a suitable statement of problem] Suggested answer: How to differentiate between magnesium nitrate solution and calcium nitrate solution // How to differentiate between magnesium ion and calcium ion [Able to make a suitable aim] Suggested answer:

SCORE 3

2

To differentiate the presence of magnesium ion and calcium ion by using aqueous ammonia solution. [Able to state an idea of statement of problem or aim]

1

No response given / wrong response

0

3(b) KK051202 – Stating hypothesis EXPLANATION [Able to state the relationship between manipulated variable and responding variable correctly] Suggested answer: If the addition of aqueous ammonia solution forms white precipitate which is insoluble in excess ammonia aqueous solution, then the solution tested is magnesium nitrate. // If aqueous ammonia solution is added and no change occur then the solution tested is calcium nitrate. [Able to state the relationship between manipulated variable and responding variable] [Able to state an idea of the hypothesis] No response given / wrong response

SCORE 3

2 1 0

3 (c) KK051202 – Stating variables EXPLANATION [Able to state all the three variables correctly] Suggested answer: Manipulated variable : magnesium nitrate and calcium nitrate // Mg2+ and Ca2+ Responding variable: formation of white precipitate Controlled variable : aqueous ammonia solution [Able to state any two of the variables correctly] [Able to state one of the variables correctly or state idea regarding variable] No response given / wrong response

19

SCORE

3(d) KK051205 – List of substances and apparatus EXPLANATION [Able to state the list of substances and apparatus correctly and completely] Suggested answer: Test tube, dropper, test tube rack 0.5 mol dm-3 magnesium nitrate solution, 0.5 mol dm-3 calcium nitrate solution, aqueous ammonia solution. [Able to state the list of substances and apparatus correctly but not completely] Suggested answer: Test tube 0.5 mol dm-3 magnesium nitrate solution, 0.5 mol dm-3 calcium nitrate solution, aqueous ammonia solution. [Able to state an idea about the list of substances and apparatus] Suggested answer: Test tube magnesium nitrate, calcium nitrate No response given / wrong response

SCORE 3

2

1

0

3(e) KK051204 – Technique /Precedure EXPLANATION [Able to state a complete experimental procedure] Suggested answer: 1. 2 cm3 of solution A is poured into a test tube. 2. A few drops of aqueous ammonia solution are added into the test tube using a dropper and the test tube is shaken well. 3. If the precipitate is formed, aqueous ammonia solution is added continuously until no further change occurred / until excess 4. The mixture is shaken well. 5. The changes occur is recorded in a table. 6. Steps 1 to 4 are repeated using solution B.

SCORE 3

[Able to state a complete experimental procedure] 1,2,3,4,5

2

[Able to state a complete experimental procedure] 1,2,3,5 No response given / wrong response

1

20

0

3(f) Tabulation of data EXPLANATION [Able to exhibit the tabulation of data correctly ] Reagent

SCORE

Observation Test tube/Solution A Test tube/Solution B

Aqueous ammonia solution

3

[Able to exhibit the tabulation of data less accurately ] Reagent Aqueous ammonia solution

Test tube /Solution A

2 Test tube/Solution B

[Able state an idea about the tabulation of data]

1

No response given / wrong response

0

END OF MARKING SCHEME

21