kimia p2 sbp mid year spm 2008
TRANSCRIPT
Nama: .................................................... Tingkatan: ..............................SULIT4541/2ChemistryPaper 2MEI20082 ½ jam
BAHAGIAN SEKOLAHKEMENTERIAN PELAJARAN MALAYSIA
PEPERIKSAAN PERTENGAHAN TAHUN 2008
FORM 5 CHEMISTRY
Paper 2
Dua jam tiga puluh minit
JANGAN BUKA KERTAS SOALAN INI SEHINGGA DIBERITAHU
1. Tuliskan nama dan tingkatan padaruang yang disediakan.
2. Jawab semua soalan daripadaBahagian A. Tuliskan jawapan andadalam ruang yang disediakan
3. Jawab satu soalan daripada BahagianB dan satu soalan daripada BahagianC.Jawapan kepada bahagian B danBahagian C hendaklah ditulis padakertas tulis.
4. Anda diminta menjawab dengan lebihterperinci untuk Bahagian B danBahagian C. Jawapan mestilah jelasdan logik. Persamaan, gambar rajah,jadual, graf dan cara lain yang sesuaiuntuk menjelaskan jawapan anda bolehdigunakan.
5. Anda hendaklah menyerahkan kertastulis dan kertas tambahan, jikadigunakan bersama-sama dengankertas soalan.
6. Penggunaan kalkulator saintifik yangtidak boleh diprogramkan adalahdibenarkan.
Bahagian Soalan Markahpenuh
Markahdiperoleh
A
1 102 103 104 105 106 10
B 7 208 20
C9 2010 20
Jumlah
Kertas soalan ini mengandungi 17 halaman bercetak[lihat sebelah
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1. Figure 1 shows the location of seven elements A, D, E, G, J, L and M in thePeriodic 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, answerthe following questions.
(a) (i) Which of the element is chemically unreactive?
………………………………………………………………………………[1 mark]
(ii) 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 isformed 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 experimentusing 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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(d) Why are elements A and L placed in the same group?
………………………………………………………………………………………[1 mark]
(e) 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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2. Graph 2.1 shows the temperature against time when solid naphthalene is heated.
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]
Temperature /0C
Time/s
T1
T0 P
Q R
S
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(d) State how the movement of naphthalene particles changes between R and Sduring heating.
………………………………………………………………………………............[ 1 mark]
(e) Table 2.2 shows four substances and their respective formulae.
Substances Chemical formula
Iodin I2
Copper CuNaphthalene C10H8
Copper(II) sulphate 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?
........................................................................................................................[ 1 mark]
(iii) 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 brownbromine vapour spreads to the upper part of the gas jar. The time taken is veryshort.Name the process occurs.
……………………………………………………………………………................[ 1 mark]
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3. Diagram 3 shows a flow chart for the industrial manufacture of compound Zfrom sulphuric acid and 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 formcompound 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]
Contact Process Sulphuric acid
Compound ZReaction X
Haber Process Ammonia
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(c)
(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]
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.
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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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(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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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
hydrogen peroxide /cm3
Concentration of hydrogen
peroxide /mol dm-3
I 20 2
II 20 4
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 betweenexperiment I and II.
……………………………………………………………………………....[1 mark]
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(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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6. Figure 6 shows the conversions of organic compound A to another substances,
C2H4(OH)2 and C2H5OH through Processes A and C.
(a) What is meant by organic compound?
………………………………………………………………………………............
………………………………………………………………………………............[1 mark]
(b) (i) Write the molecular formula of compound A.
………………………………………………………………………............[1 mark]
(ii) Name the compound A.
………………………………………………………………………............[1 mark]
(iii) Identify a functional group of compound A.
………………………………………………………………………............[1 mark]
Process C
Process A
Reagent B
Steam
C2H4(OH)2
C2H5OH
Compound A
Diagram 6
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(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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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.
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) element X and element Y.ii) element Y and element Z.
[12 marks]
(c) The melting point of magnesium oxide is much higher than methylbenzene.
Explain why.
[6 marks]
23
X11
35
Y17
12
Z6
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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 is70 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 theprosedure to determine the empirical formula of Z oxide. The procedureshould included a precaution.
[10 marks]
(ii) Diagram 8 shows the result obtain in c(i).
Diagram 8
Based on the information in Table 8, determine the values of the following :[Relative atomic mass : O=16 , Z=65]
i) mass of leadii) number of moles of leadiii) mass of oxygeniv) number of moles of oxygenv) empirical formula of lead oxide
[5 marks]
Mass of crucible + lid, g = 46.30Mass of crucible + lid + Z, g = 46.30Mass of crucible + lid + Z oxide, g = 46.62
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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.
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]
O
H C O H
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10. Diagram 10.1 shows how compound M is formed from ethanoic acid and
propanol.
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 naturalcondition
Latex coagulates
Ammonia solution is added tolatex
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
ConcentratedH2SO4
ethanoic acid + propanol
Compound M
1
SULIT 4541/1/2/34541ChemistryMarking SchemeMei2008
BAHAGIAN SEKOLAHKEMENTERIAN PELAJARAN MALAYSIA
______________________________________________PEPERIKSAAN PERTENGAHAN TAHUN 2008
FORM 5 CHEMISTRY
MARKING SCHEME FOR PAPER 1, 2 AND PAPER 3
Peraturan pemarkahan ini mengandungi halaman bercetak.
2
PAPER 1
1 B 21 D 41 D2 C 22 D 42 B3 B 23 B 43 D4 C 24 A 44 C5 D 25 C 45 B6 A 26 A 46 A7 B 27 D 47 B8 A 28 A 48 D9 D 29 C 49 C
10 D 30 A 50 B11 D 31 A12 C 32 B13 A 33 D14 A 34 A15 C 35 C16 B 36 A17 C 37 D18 C 38 B19 C 39 B20 C 40 D
3
PAPER 2-SECTION A
No. Rubric Mark
1 a
b (i)
(ii)
c
d
e (i)
(ii)
(iii)
G
Has stable /octet electron arrangement//8 valence electron
2A + 2H2O 2AOH + H2
Use a small pieces//use a forcep// use a google
G,E,D, A,J,L
Has same valence electron// valence electron is 1
DE2 r: E2D
[can draw the diagram of electron arrangement correctly]
- Correct structure of atoms
- Correct ratio of atoms=1:2
Has (neutral ) molecule
TOTAL
1
1
1
1
1
1
1
2
1
10
2 a
b(i)
(ii)
c
d
e (i)
(ii)
(iii)
T1
PQ: solid + liquid
RS: liquid
Heat energy absorbed
is used to overcome the forces of attraction between particles
// Heat is absorbed to overcome the intermolecular forces
r: ion/atom
(1+1)
The particles / molecules move faster
Iodine/I2//napthalene/C10H8
Copper/ Cu
Ion
Diffusion
TOTAL
1
1
1
1
1
1
1
1
1
1
10
4
3 a (i)
(ii)
b (i)
(ii)
(iii)
c (i)
(ii)
d
3H2 + N2 2NH3
( Extract from ) air
Neutralization
H2SO4+ 2NH3 (NH4)2SO4
//H2SO4+ 2NH4OH (NH4)2SO4 + H2O
Fertilizer
Tin
In pure copper the layer of atom are easily slide over each
other when external force is applied on them.
The different size of foreign atoms in allloy are prevent the
layers of atom from slide each other when external force is
applied.
TOTAL
1
1
1
1
1
1
(1+1)
1
1
10
4 a
b(i)
(ii)
1 Diagram of set up of apparatus complete and functional
2 Label
(Anode) – impure copper and (cathode )– pure copper
3 ( Electrolyte) – copper (II) sulphate / copper (II) chloride // copper
(II) nitrate solution
a: chemical formula
1 become thinner // decrease in mass
2 become thicker // increase in mass
1 ( Remain )unchanged
2 Number of Cu2+ ions produced at anode same as number of
copper atoms produced at cathode // the rate of formation of Cu2+
1
1
1
1
1
1
Copper atomCopper atom
Tin atom
5
c (i)(ii)
d
ions at the anode is the same as the rate of discharge of Cu2+ at
cathode.
(Anode ):Cu Cu2+ + 2e
(Cathode ): Cu2+ + 2e Cu
Electroplating of metals/ Extraction of reactive metals
TOTAL
1
1
1
1
10
5 a
b
c (i)
(ii)
d
2H2O2 O2 + 2H2O
Number of mole of H2O2 = 20 x 2/1000= 0.04
2 mol of H2O2 produce 1 mol of O2 //
Number of mole of O2 = 0.04/2 = 0.02
Volume, O2 = 0.2 x 24dm3 = 4.8 dm3
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
The frequency of collision between H2O2 molecule is higher
The frequency of effective collision is higher
Volume of gas/cm3
Time(s)
Label Y axes and X axesCorrect curve and label I and II
TOTAL
1
1
1
1
1
1
1
1
11
10
II
I
6
6 a
b (i)
(ii)
(iii)
c (i)
(ii)
(iii)
d (i)
(ii)
(iii)
A compound that contain element of carbon and derive from living
organisms.
C2H4
ethene
double bond between carbon atoms
(a: C=C )
Acidified potassium manganat (VII) // Acidified potassium
dicromate (VI)
Oxidation
Purple to colourless // orange to green
C2H4 + H2O C2H5OH
Alcohol
Temperature 300 oC // Pressure 60 atmosphere // concentrated
phosphoric acid
TOTAL
1
1
1
1
1
1
1
1
1
1
10
7
SECTION B
No. Rubric Mark
7 a (i)
(ii)
b
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
Compound that form between non metal atom by sharing their
valence electron to achieve stable/octet /duplet electron
arrangement
Between P and Q
Atom X has 1 valence electron
Atom X loses/donates/transfers 1 electrons to form X+ ion //
XX+ + e- and attain stable octet electron arrangement
Atom Y has 7 valence electrons
Atom gains/receives/accept 1 electron to formY- ion//
Y + e-Y-
attain the stable /octet electron arrangement
The two oppositely-charged ions// the X+ and Y- ion are
bonded together by a strong electrostatic force
To form a ionic compound with the formula XY// diagramn
Max 7
1
1
1
1
11
1
11
X
Y
8
(ii)
(iii)
Between Y and Z
Atom Z has 4 valence electrons and atom Y has 1 valence
electrons
One atom Z contributes 4 electrons and (each) atom Y
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
Magnesium oxide is an ionic compounds
Strong electrostatic force of attraction exists between
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
Tetrachloromethane is a covalent compound
Weak intermolecular forces //held together by weak (Van der
Waals) force of attractions between molecule
little heat energy //low energy is needed to overcome the
weak forces
1
1
111
1
1
1
1
1
1
Z YY
Y
Y
9
8 a
b
c(i)
Empirical formula- Formula shows simplest ratio of atoms of each
element in the compound
Molecular formula- Formula shows actual number of atoms of
each element in the compound
Molecular Formula = ( Empirical formula )n= ( CH2 )n
Relative Molecular Mass ( CH2 )n = 7012n + 2n= 7014n=70
n=5
Molecular Formula C5H10
1. Metal Z is cleaned using sand paper
2. A crucible and its lid are weighed and the mass is recoded
3. Metal Z is palced in the crucible. The crucible,lid and its
content is weighed and the mass is recorded.
4. The crucible with its content is heated strongly without
lid.
5. When metal Z start burn, the crucible is covered by its
lid
6. the covered is raise a little at intervals
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
Content and record the mass.
9. The process of heating, cooling and weighing is repeated
until constant is obtained.
10. (Precaution step );
Close the crucible immediately to prevent loss of
1
1
1
11
11
1
1
1
1
1
1
1
1
TOTAL 20
10
Element Z O
Mass(g) 1.30 0.32
mol 1.30/65=0.02 0.32/16=0.02
Simplestratio
1 1
Empirical Formula ZO
TOTAL
1
1
1
1
1
20
11
PAPER2 –SECTION C
No Rubric Mark
9 a
b (i)
(ii)
c(i)
Sample answer :
Zn + HNO3 Zn(NO3)2 + H2O
ZnCO3 + HNO3 Zn(NO3)2 + H2O + CO2
ZnO + HNO3 Zn(NO3)2 + H2O
Any two
Methanoic acid partial ionizes in water
produce low concentration of hydrogen ion
Glacial ethanoic acid has (neutral) molecule
Methanoic acid aqueous ionizes in water
to produce free moving ion
Procedure :
1 100 cm3 of 0.1 moldm-3 sulphuric acid is poured into a beaker
and heated slowly.
2 zinc carbonate is added into the sulphuric acid until in excess/nolonger dissolves.
3 Stir the solution and filtered.
4 The filtrate is poured into an evaporating dish and heat untilsaturated
5 The hot saturated salt solution is allowed to cool
6 The crystals formed are filtered out, rinsed with distilled water
7 dried between sheets of filter paper.
2
1
1
1
1
1
1
1
1
1
1
1
12
(ii)
d
ZnCO3 + H2SO4 ZnSO4 + H2O + CO2
Number of mole , H2SO4 = 0.1( 100 )/1000
= 0.01
1 mol of H2SO4 produce 1 mol of ZnSO4
Mole of ZnSO4 = 0.01
Mass of ZnSO4 = 0.01 X 161
= 16.1 g
Sample answer :
1 ammonium chloride as a fertilizer2 copper (II) sulphate as a pesticide3 hydrated calcium sulphate to make plaster casts4 sodium chloride food additive
Any 2 suitable anwers(1+1)
TOTAL
1
1
1
1
1
1
20
10a (i)
(ii)(iii)
(iv)
(v)
catalyst
esterification
CH3COOH + C3H7OH CH3COOC3H7 + H2O
Correct reactant
Correct product
Ethyl propanoate
Sweet smell/fruity smell/fragrant smell
//insoluble in water/soluble in organic solvent
//colourless
//less dense than water
any two properties (1+1)
1
1
1
1
2
2
13
b (i)
(ii)
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
Rubber polymer are released and lump together
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
The presence of cross-linkage of sulphur atoms between
the rubber molecule
When vulcanized rubber is stretched and release, the cross-
linkage will pull the chain back to their original
arrangement
Diagram
Improves the elasticity and strength of the rubber / make
vulcanized rubbers more resistant to heat /organic solvent
orResistant to oxidation :
The presence of cross-linkage of sulphur atoms between
the rubber molecule
Diagram
C=C in vulcanized rubber is less than C=C in the
unvulcanized rubber,
so vulcanize rubber is more resistant to oxidation
TOTAL
1
1
1
1
1
1
1
1
1
1
1
1
1
1
20
14
PAPER 3
1 (a) KK0503 – Measuring and using numbersEXPLANATION SCORE
[Able to write all the times with units accurately]Suggested answer:
t1 55.0 s, t2 48.0 s , t3 42.0 s , t4 37.0 s , t5 33.0 s
3
[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- ObservationEXPLANATION SCORE
[Able to state the colour of sulphur and the rate of it is formed]Suggested answer:
Pale / light yellow precipitate is slowly formed
3
[Able to state the colour of sulphur]Pale / light yellow precipitate is formed.
2
[Able to state the formation of precipitate]A precipitate is formed.
1
No response given / wrong response 0
1 (c) KK0506 – CommunicatingEXPLANATION SCORE
[Able to construct a table correctly containing three labeled columns withcorrect units and record all the time and 1/time accurately ]
Suggested answer:
Temperature,o C
30 35 40 45 50
Time , s 55.0 48.0 42.0 37.0 33.0
1 / time , s-1 0.018 0.021 0.024 0.027 0.030
3
[Able to construct a table correctly containing three labeled columns withcorrect 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
15
EXPLANATION SCORE[Able to draw a graph accurately that consists of the following aspects]Suggested answer:
1. Both axes labeled and units( Y axis - temperature , X axis – 1/ time )
2. All points transferred correctly3. Uniform scale, graph size covers at least half of the graph paper.4. Straight line/ best fits drawn
3
[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 correctly3. 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 OperationallyEXPLANATION SCORE
[Able to interpret the relationship between the rate of reaction and thetemperature of sodium thiosulphate solution from graph accurately]Suggested answer:
The rate of reaction is directly proportional to the temperature of sodiumthiosulphate solution // As the temperature of sodium thiosulphate increasesthe rate of reaction increases.
3
[Able to interpret the relationship between the rate of reaction and thetemperature of sodium thiosulphate solution from graph ]
The rate of reaction is proportional to the temperature // the temperature isproportional to the rate of reaction // the rate of reaction increases when thetemperature increases.
2
[Able to state an idea of hypothesisThe temperature affects the rate of reaction.
1
No response given / wrong response 0
16
30
35
40
45
50
0.015 0.020 0.025 0.030X
X
X
X
X
Temperature /oC
1/time , s-1
17
1(e) KK0510 - State variables
EXPLANATION SCORE[Able to state three variables and three action to be taken]Suggested answer:
Variable Action to be takenManipulated:Temperature
Heat the sodium thiosulphatesolution at different temperature //Use different temperature.
Responding:Rate of reaction / time taken for “X”marks to disappear from view.
Record the time taken for “X” markto disappear from view.
Controlled :Concentration and volume of H2SO4,concentration and volume of sodiumthiosulphate solution, size of conicalflask.
Use the same concentration andvolume of H2SO4 /sodiumthiosulphate solution // Use samesize conical flask.
3
[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 CommunicatingEXPLAINATION SCORE
[Able to write the correct overall ionic equation]Suggested answer:
Mg + Cu2+ Mg2+ + Cu
3
Mg + CuSO4 MgSO4 + Cu 2Mg Mg2+ + 2e // Cu2+ + 2e Cu 1No response given / wrong response 0
2(a)(i) KK 0504 – Making inferenceEXPLANATION SCORE
[Able to state the correct inference]Suggested answer:
Magnesium atom releases/donate/loses electrons to produce magnesium ion //Magnesium is corrode.
3
Magnesium becomes thinner // mass of magnesium decreases 2Magnesium dissolves 1No response given / wrong response 0
18
2(b) KK 0505 - PredictingEXPLANATION SCORE
[Able to state the voltage value]0.65 V
3
0.63 – 0.64 V // 0.66 – 0.67 V 2< 0.64 V // > 0.67 V 1No response given / wrong response 0
2(c)KK 0508 – Interpreting DataEXPLANATION SCORE
[Able to arrange the position of all metals in an ascending order based ontendency to release electrons correctly]Copper > Lead > Iron > Zinc > Magnesium
3
[Able to arrange the position of all metals in descending order based ontendency to release electrons]Magnesium > Zinc > Iron > Lead > copper
2
[Able to arrange the position of at least four metals in ascending order basedon tendency to release electrons correctly]
1
No response given / wrong response 0
2(d) KK0509 – Operational definitionEXPLANATION SCORE
[Able to state the correct and complete operational definition]Suggested answer:
The further the metal is from copper in the electrochemical series, the greateris their voltage reading. //
3
[Able to give incomplete relationship]Suggested answer:
The further apart the metal is in the electrochemical series, the greater thepotential difference / voltage reading.
2
[Able to state an idea]Suggested answer:
The position of metal influence the voltage reading //Type of metal influence the voltage reading.
1
No response given / wrong response 0
19
3.(a) KK051021 – Statement of problemEXPLANATION SCORE
[Able to make a suitable statement of problem]Suggested answer:
How to differentiate between magnesium nitrate solution and calcium nitratesolution // How to differentiate between magnesium ion and calcium ion
3
[Able to make a suitable aim]Suggested answer:
To differentiate the presence of magnesium ion and calcium ion by usingaqueous ammonia solution.
2
[Able to state an idea of statement of problem or aim] 1
No response given / wrong response 0
3(b) KK051202 – Stating hypothesisEXPLANATION SCORE
[Able to state the relationship between manipulated variable and respondingvariable correctly]Suggested answer:
If the addition of aqueous ammonia solution forms white precipitate which isinsoluble in excess ammonia aqueous solution, then the solution tested ismagnesium nitrate. // If aqueous ammonia solution is added and no changeoccur then the solution tested is calcium nitrate.
3
[Able to state the relationship between manipulated variable and respondingvariable]
2
[Able to state an idea of the hypothesis] 1
No response given / wrong response 0
3 (c) KK051202 – Stating variables
EXPLANATION SCORE[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 precipitateControlled 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
20
3(d) KK051205 – List of substances and apparatusEXPLANATION SCORE
[Able to state the list of substances and apparatus correctly and completely]Suggested answer:
Test tube, dropper, test tube rack0.5 mol dm-3 magnesium nitrate solution, 0.5 mol dm-3 calcium nitratesolution, aqueous ammonia solution.
3
[Able to state the list of substances and apparatus correctly but notcompletely]Suggested answer:
Test tube0.5 mol dm-3 magnesium nitrate solution, 0.5 mol dm-3 calcium nitratesolution, aqueous ammonia solution.
2
[Able to state an idea about the list of substances and apparatus]Suggested answer:
Test tubemagnesium nitrate, calcium nitrate
1
No response given / wrong response 0
3(e) KK051204 – Technique /Precedure
EXPLANATION SCORE[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 excess4. The mixture is shaken well.5. The changes occur is recorded in a table.6. Steps 1 to 4 are repeated using solution B.
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
1
No response given / wrong response 0
21
3(f) Tabulation of dataEXPLANATION SCORE
[Able to exhibit the tabulation of data correctly ]
Reagent ObservationTest tube/Solution A Test tube/Solution B
Aqueousammonia solution 3
[Able to exhibit the tabulation of data less accurately ]
Reagent Test tube /Solution A Test tube/Solution BAqueousammonia solution
2
[Able state an idea about the tabulation of data] 1
No response given / wrong response 0
END OF MARKING SCHEME