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Peraturan Permarkahan
Chemistry
Kertas 2
Okt/Nov 2012
MPSM PAHANG
PEPERIKSAAN PERCUBAAN SPM TAHUN 2012
TINGKATAN 5
CHEMISTRY
Kertas 2
PERATURAN PEMARKAHAN
Amaran
Peraturan pemarkahan ini adalah SULIT.
_____________________________________________________________________
Kertas skema ini mengandungi 10 halaman bercetak
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MARKING SCHEME / SKEMA PERMARKAHAN
CHEMISTRY PAPER 2
TRIAL SPM MPSM PAHANG 2012
NO
Answers
Marks
1.a)
C3H6
1
b)(i)
CnH2n+1 OH
1
(ii)
C3H7OH
c)
H H
C3H6 + H20
H
1
H H
H
H- C –C- C - H
H – C – C – C -O H
H H
1+1
H
H OH H
Propan-1-ol
Propan-2-ol
(any one)
d)(i)
Propane
(ii)
C3H6 + H2
e)(i)
1
C3H8
-Formula reactant correct
1
-Formula product correct
1
Propyl ethanoate
1
9
2.a)
(i)
Number of proton in nucleus of its atom
1
(ii)
15
1
b)
Nucleon number
1
Q and R have different number of neutron/nucleon number
1
Carbon 14 - to estimate the age of fossils and artifacts
1
c)(i)
(ii)
Cobalt 60 - kill cancer cells,sterilised medical instruments
Sodium 24-detect leakage of underground pipes
(any one)
d (i)
2.8.7
1
(ii)
7
1
iii)
Draw diagram:
-
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R
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3
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Figure of electron arrangement of R
1
3 shells
1
9
3.a)
( i)
Z
1
(ii)
Q
1
(iii)
Y
1
b)
Q, P, Z, Y, T
1
c)
4
1
d)
Z has higher number of protons than T. Hence it has stronger
1+1
nuclei attraction on the electrons.
e)
Y3+
1
f)
Transition Elements
1
g)
Their ions or compounds are colored//They form complex
1
ions or compounds/they are good catalysts//They can have
variable oxidation.
10
4.a)
b.(i)
(ii)
H+ , Cu 2+ ,
1
SO42- , OH -
1
Bubbles of gas released
Concentration of Cu
2+
decrease // Cu
1
2+
1
discharge to form Cu atom
(c)
d)(i)
Cu2+ + 2e
Cu
Anode become thinner / smaller / mass
1
1
decrease
(ii)
Cathode become thicker / bigger / mass
1
increase
e)
Correct diagram
1
Copper electrode at anode
Steel spoon at cathode
Copper (II) sulphate as electrolyte
Correct label
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f)
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Hydroxide ion
1
10
5.a)
b)
Pink to colourless
1
The point in the titration at which the indicator changes
1
colour
1+1
c)
H2SO4 + 2NaOH
d)
Sodium sulphate and water
1
e)
M1V1 = 1
M2V2
2
1
0.25 × V1 = 1
0.5 × 25
2
1
Na2SO4 + 2H2O
V1 = 1 × 0.5 × 25
2 × 0.25
1
= 25cm3
f)
50 cm3
g)
i) Vinegar is used to cure wasp sting that alkaline in nature
1
ii) Toothpaste contain bases to neutralize acid produce by
1+1
bacteria
11
6.
a)
Redox reaction is a reaction in which oxidation and reduction
1
occur at the same time
b)
Oxygen and water
1
c)
Fe → Fe2+ + 2e
1
d)
Label of water droplet, oxygen and iron
1
Label of anode and cathode
1
Draw arrow from negative to positive pole iron
1
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e)
f)
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Electron transfer form anode to cathode
1
Oxygen in water gains electrons
1
Hydroxide ion is form
1
Using sacrificial metal // sacrificial protection /
By alloying /
By tin platting /
By galvanizing
(Any two)
1+1
11
7
height of precipitate/ cm
a)
6
5
4
3
2
1
0
1
2
Correct axis with unit
Correct and Smooth line
Correct scale
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4
5
6
7
1
1
1
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b.
(i)
(ii)
c)
d.(i)
(ii)
iii)
Pb(NO3)2 + 2KI  PbI2 + 2KNO3
1+1
Volume of Pb(NO3)2 = 2.5 cm3
1
No of mole Plumbum (II) ion = 1 x 0.0025 = 0.0025 mol
1
No of mole iodide ions = 2 x 0.0025 = 0.005 mol
1
Pb2+ +2 I-
PbI2
Correct reactants and products
1
Balance equation
1
Salt X = Copper (II) carbonate
1
Gas Z = Carbon dioxide
1
Y precipitate = Barium sulphate
1
CuSO4 + Ba(NO3)2  Cu(NO3)2 + BaSO4
Correct reactants and products
1
Balance equation
1
1. Add sodium hydroxide solution.
1
+
2. Blue precipitate formed indicates the presence of Cu ion.
1
3. Add hydrochloric acid.
1
4. Add barium chloride solution.
1
5. White precipitate formed indicate the presence of SO42-
1
ion.
20
8.
a)
1. the mixture becomes hot
2. the thermometer reading increase
3. zinc powder dissolves
4. brown solid/precipitate formed
5. the blue solution turn colourless
(Any three)
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(b)(i)
(ii)
(iii)
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Cu 2+ + Zn
Cu + Zn2+
-Correct formula & reactants
-correct balance
1
1
Heat released in the reaction
-50x4.2x5// 1050 J
-number of mol of Cu atom
50x0.1//0.005 mol
1000
-show the step to obtain heat of displacement
1050 J
0.005 mol
- heat of displacement with unit and negative symbol
-210000 Jmol-1//-210 kJmol-1
1
1
1
1
1
-heat loss to the surrounding
2 precautions
1. use polysterene cup//use two layers of polysterene cup
Instead of one.
2. add zink powder quickly into the solution
3. stir the mixture continuously until highest temperature
obtained.
(Any two)
(iv)
- temperature change will be doubled//100C
- number of copper(II) ions per unit is doubled/ two times
higher
1+1
1
1
1
c) (i)
Label Energy, correct level of reactants & product
- correct chemical equations
H with negative symbol and unit
1
1
Zn + Cu2+
H= - 210 kJ mol-1
Energy
Zn2+ + Cu
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(ii)
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
Exothermic reaction//heat released to the surrounding
1

Energy content of reactants is higher than energy
1
content of products

Heat absorbed to break down the bond is lower than
1
heat released to form a bond
20
9
a.(i)
1. Tomato puree is used as a colouring agent to restore the
colour of the food.
2. Sugar // spice is used as a flavouring agent to enhance
the taste of food
3. Permitted modified starch is used as thickener to thicken
2+2
food.
(Any two)
(ii)
Advantage :
i) to prevent food from spoilage
1
ii) to improve appearance, texture or taste
Disadvantage:
i) Lead to serious diseases like asthma, and cancer
b.
1
- Part A is hydrophobic: Soluble in oil or grease
1+1
1+1
- Part B is hydrophilic: Insoluble in oil or grease//soluble in
water
c.
1. Hard water contain Mg2+ and Ca2+ ion
1
2. Detergent does not form scum in hard water
1
3. Soap form scum in hard water
1
4. Mg2+ and Ca2+ in hard water react with soap
1
5. Soap molecule consist of hydrophobic and hydrophilic
part
1
6. Hydrophobic part dissolve in oil
1
7. Hydrophilic part dissolve in water
1
8. During scrubbing/rinsing the oily stains/spots is
1
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washed away
9. Cloth in experiment II /detergent is cleaner than cloth
in experiment I
1
10. Detergent in hard water is more effective than soap.
1
20
10.
a.(i)
The speed at which reactant are converted into product in a
1
chemical reaction// change in selected quantity of reactant or
produrt per unit of time taken.
(ii)
Total surface area / concentration of reactant / temperature
1+1
of reactant / use of catalyst / pressure of gaseous reactant
(any 4)
b)
c)
To make the coffee powder and sugar dissolve easier in
water.
1
The heat given to the water will give more kinetic energy to
the particles.
1
The particles of water, coffee powder and sugar move faster.
1
They will collide each other more frequent.
1
The frequency of effective collision will increase.
1
Precipitate : Sulphur
1
Materials:
0.2 mol dm-3 sodium thiosulphate, 1.0 mol dm-3 sulphuric
acid, a piece of white paper marked ‘X’ at the centre.
1
Apparatus:
150 cm3 conical flask, stopwatch, 50 cm3 measuring cylinder,
10 cm3 measuring cylinder, thermometer, Bunsen burner,
wire gauze.
1
Procedure:
Using a measuring cylinder, 50 cm3 of 0.2 mol dm-3 sodium
thiosulphate solution is measured and poured into a conical
flask.
The conical flask is placed on top of a piece of white paper
marked ‘X’ at the centre.
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5 cm3 of 1.0 mol dm-3 sulphuric acid is measured using
another measuring cylinder.
1
The sulphuric acid is poured immediately and carefully into
the conical flask. At the same time, the stop watch is atarted
1
The mixture in a conical flask is swirled.
1
The ‘X’ mark is observed vertically from the top of the conical
flask through the solution.
1
The stopwatch is stopped once the ‘X’ mark disappears from
view.
1
Step 1 – 7 are repeated using 50 cm3 of 0.2 mol dm-3 sodium
thiosulphate solution at 40oC, 50oC, 60 oC by heating the
solution before 5 cm3 of sulphuric acid is added in.
(Max 8)
1
Conclusion
The increase of temperature, increase the rate of reaction
1
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END OF MARKING SCHEME
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