Kimia Scheme Copy
Transcript of Kimia Scheme Copy
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Kimia
Skema Pemarkahan
September
2009
PERSIDANGAN KEBANGSAAN PENGETUA-PENGETUA
SEKOLAH MENENGAH MALAYSIACAWANGAN KELANTAN
PEPERIKSAAN PERCUBAAN 2009
SIJIL PELAJARAN MALAYSIA
KIMIA
SKEMA PEMARKAHAN
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PEPERIKSAAN PERCUBAAN SPM 2009
CHEMISTRY MARKING SHEME
4541
ANSWER OF PAPER 1
No. Answer No. Answer
1 B 26 A
2 B 27 B
3 D 28 C
4 C 29 C
5 C 30 A
6 D 31 A
7 D 32 C
8 C 33 A
9 A 34 B
10 A 35 B
11 B 36 B
12 D 37 B
13 B 38 C
14 B 39 D
15 C 40 A16 D 41 D
17 A 42 D
18 D 43 C
19 B 44 C
20 C 45 A
21 D 46 B
22 A 47 B
23 A 48 B
24 D 49 A
25 B 50 A
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MARKING SCHEME OF PAPER 2
MARKQUESTION NO Marking Criteria
SUB TOTAL
(a) (i) Alkali 1
(ii) OH- 1
(iii) 7 < pH
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(d) To allow the flow of ion from both electrolyte through it to
complete the circuit
1
(e) The zinc plate becomes thinner 1
(f) Cu2+ + 2e Cu 1
(g) (i) The voltage will be higher 1(ii) The silver metal is under the copper metal in the electrochemicalseries.
1
(h)
A B C
1
1
(a) (i) The chemical formula that shows the simplest ratio of atoms of theelements present in a compound.
1
(b) (i) ElementUnsur
Mg O
Mass (g) 25.12 24.88
//0.24
25.28 25.12
//0.12
Number of
moles
0.24/24 // 0.01 0.16/16 // 0.01
Simplest ratio of
moles1 1
Empirical
formulaMgO
1+1
1+1
1
1
(ii) 2Mg + O2 2MgO 1
(c) To ensure that all the magnesium reacts completely with
oxygen.
1
4
(d) Copper is an unreactive element towards oxygen 1
10
(a) Acidified Potassium manganate(VII) 1(b) +7 1
(c) reduction 1
(d) (i) Colourless solution turn brown 1
(ii) 2I-
I2 + 2e 1
(iii) Iodide ion release electron 1
(e) To allow the flow of ion from both electrolytes 1
5
(f) Functional diagram of simple cell
Label
1
1
9
0.1
0.8For pair of metal A / B ,the voltage produced
= 0.8 0.1 = 0.7 V
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(a) (i) Butanol 1
(ii) The heat given off when 1 mol of butanol burn completely in
excess oxygen is 2679 kJ.
1
(b) (i) (1) Number of mole = 0.37 mol //0.005 mol
74(2) Heat released = 0.005 x 2679/ 13.395 kJ/13.395 x 103 J
1
1
(ii) (1) Substitution/Replacement
13.395 x 103
= 500 x 4.2 x
/ = 13.395 x 103
500 x 4.2
(2) = 6.379/6.40C
1
1
(c) Draw and label of the energy axis in the form of arrow with
two level of energyFormula/Name the reactants and products for exothermic
reaction
Energy C4H9OH + 6O2
H = -2679 kJmol-1
4CO2 + 5H2O
1+1
(d) (i) Any value between: -2016 kJ mol-1 H - 2036 kJ mol-1 1
6
(ii) As the number of carbon atoms increases, there are more
carbon dioxide and water molecules are produce
Thus more bonds are formed
1+1
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Section B
Marking Criteria MARKQUESTIONNO SUB TOTAL
7. (a) 12 represents the nucleon number.
6 represents the proton number.
1
1 2
(b) Able to draw the structure of an atom elements X.
The diagram should be able to show the following informations:
1. correct number and position of proton in the nucleus/ at the
centre of the atom.
2. correct number and position of neutron in the nucleus/ at the
centre of the atom.
3. correct number and position of electron circulating the
nucleus
4. correct number of valence electrons
Sample answer:
1
1
1
1 4
e
-
e-
e-
e-
e-
e
-
e-e-
e-
e-
e-
11p
12n 1
2
3
4
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or
(c) (i) Atoms W and Y form covalent bond.
To achieve the stable electron arrangement,
atom W contributes 4 electrons while atom Y contributes one electronfor sharing.
Thus, atom W shares 4 pairs of electrons with 4 atoms of Y,
forming a molecule with the formula WY4// diagram
1
1
11
1
(ii) Atom X and atom Y form ionic bond.
Atom X has the electron arrangement 2.8.1. and atom Y has the
electron arrangement 2.8.7.
1
1
Y
Y
Y
WY
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
11p + 12n
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To achieve a stable (octet )electron arrangement,
atom X donates 1 electron to form a positive ion // equation
X X+ + e
Atom Y receives an electron to form ion Y-//equationand achieve a
stable octet electron arrangement.Y + e Y-
Ion X+ and ion Y- are pulled together by the strong electrostatic forces
to form a compound with the formula XY// diagram
1
11
1
Max
10
(d) The melting point of the ionic compound/ (b)(ii) is higher than that of thecovalent compound/ (b)(i) .
This is because in ionic compounds ions are held by strong electrostatic
forces.
High energy is needed to overcome these forces.
In covalent compounds, molecules are held by weak intermolecular forces.
Only a little energy is required to overcome the attractive forces.
OR
The ionic compound/(b)(ii) conducts electricity in the molten or aqueous state
whereas the covalent compound/(b)(i) does not conduct electricity.
This is because in the molten or aqueous state, ionic compounds consist of
freely moving ions
carry electrical charges.
Covalent compounds are made up of molecules only
1
1
1
1
1
or
1
1
1
1
1
max
4
Total 20
X Y
+ -
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8 (a) (i) 1. The brown colour of bromine water becomes colourless.
2. Ethene has undergone an addition reaction.
(ii) 1. The product is 1,2-dibromoethane
2.
C C
1
1
1
1 4
(b) (i) 1. % mass of hydrogen = 100 82.75 = 17.25
2. Moles ratio of C : H = 82.75/12 : 17.25/1
3. = 2 : 5
4. The empirical formula of Z is C2H5
(ii) 1. Let the molecular formula be (C2H5)nTherefore, (12x2 + 1x5)n = 58
n = 2
2. Hence, Z is C4H10
1
1
1
1
1
11 7
(c)Property Unvulcanised rubber Vulcanised rubber
(i) Elasticity Less elastic.
Reason: the rubber
molecules can slide
over each other easily
when it is stretched.
More elastic.
Reason: the presence of
sulphur cross-links can pull
back the rubber moleculesto their original positions
after it is stretched.
(ii) Strength andhardness
Soft and less strong.Reason: the rubber
molecules can slide
over each other easily
when it is stretched.
Stronger and harder.Reason: the presence of
sulphur cross-links make
sliding of rubber molecules
more difficult.
(iii) Resistance
towards
oxidation
Easily oxidised by
oxygen.
Reason: the number ofcarbon-carbon double
bonds, C=C per
molecule is high.
More resistance to
oxidation.
Reason: the number ofcarbon-carbon double
bonds, C=C per molecule
is low.
1
1+1
11+1
1
1+1 9
Total 20
Br Br
H
H H
H
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Section C
9 (a) Food additives How food additives reactsFlavouring makes food tastier
Colouring colours food so that it looks more
AttractivePreservative Prevent the growth of microorganism
on food
Antioxidant slow down the oxidation of food
* any three from above
1 + 1
1 + 1
1 + 1
1 + 1
(b)(i)
Sample answer;
Apparatus:- 1 kg weight
- ruler
- retort stand and clamp
- thread
- steel ball
Materials:
- copper block
- bronze block
Able to state the steps:
1. a steel ball is stuck onto the copper block
2. a weight of ( -2 ) kg is hung at a height of (0.5-1)m from the top of
Copper block.
3. the weight / thread is released / dropped
4. the diameter of dent is recorded
5. step 1 to 4 are repeated several times to obtain an average of the
diameter .6. the experiment is repeated using a bronze block.
Able to construct the table:
Experiment 1 2 3 Average
diameter/mm
Diameter of dent on the copper block / mm A1 A2 A3 A
Diameter of dent on the bronze block / mm B1 B2 B3 B
Able to state the conclusion :
B is smaller than A.
Brass is harder than copper / alloys are harder than pure metals
1
1
1
1
1
1
1
1
1
1
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(c)
-Correct draw the arrangement of atom in copper
-Correct draw the arrangement of atom in bronze
-correct labeled of atom
The stanum atom distrupt the orderly arrangement of atoms in copper
This prevents the layers of pure metal (copper) atoms from sliding on one another easily.
1
1
1
11
10 (a) Able to state
(i) Sulphuric acid
Mg + H2SO4 MgSO4 + H2
(ii) Able to draw an energy profile diagram that shows the following fiveinformation:
1. label of energy on vertical axis
2. The position of the energy level of the reactant is higher than theenergy level of the product
3. Correct position of Ea
4. Correct position of Ea
5. Correct position of H
If energy level diagram given, not energy profile diagram, award pt1 and pt2
only)
1
1
1
1
1
1
1
Able to give explanation by stating the following information:
1. Reaction is exothermic
2. The reactants contain moare energy than the products
3. Heat given nout during bond formation is greater than heat
absorbed during bond breaking
4. H is the energy difference between the reactants and products
5. Activation energy, Ea must be overcome in order for the reaction
to take place
6. The use of catalyst reduces the activation energy 5
Tin/
stanum
Copper
CopperCopper
bronze
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(must correspond to the energy profile diagram: negative
catalyst increases the activation energy)
7. the use of catalyst increases the frequency of effective collision
between H+ ion and magnesium atom
(Neagative catalyst reduces the frequency of effective collision
between H+
and magnesium atom)
any five points:
Note: If endothermic reaction: Pts 1,2,3 lost
(b) (i) Able to calculate the average rate of reaction
1. volume divided by time
2. Correct answer with the unitAvarage rate of rfeactiuon = 400 cm3
200 s
= 2 cm3
s-1
1+
1
(ii) Able to explain the difference in the rate of reaction by stating the
following
Information
1. The rate of reaction for Experiment II is higher/greater than
Experiment I
r: slower/faster
2. This is because sulphuric acid in Experiment II is
diprotic/dibasic acid3. Hydrochloric acid in Experiment I is monoprotic/monobasic
acid(Basicity of acid in Experiment II is higher than acid in
Experiment I gives pts 2 and 3)
4. Diprotic acid has higher concentration of H+
ion //monoprotic
acid has lower concentration of H+
ion
a: more/higher number/less H+
5. The frequency of collision between H+
ion and magnesium in
Experiment II is higher than in Experiment I// The frequency of
collision between H+ ion and magnesium in Experiment I islower than in Experiment II
r: between particles
6. The frequency of effective collision in Experiment II is
higher/greater than in Experiment I// The frequency of effective
collision in Experiment I is lower/smaller than in Experiment II
1
1
1
1
1
1
6
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[No response given or wrong response] 0
Question Explanation Maximum
score
[Able to state the relationship between the manipulated variable and the
responding variable with direction correctly]
Sample answer:
The lower the position of an alkali metal in the Periodic Table, the more
reactive it is when reacts with oxygen.
3
[Able to state the relationship between the manipulated variable and the
responding variable]
Sample answer:
The lower position of an alkali metal in the Periodic Table, the more
reactive is the metal.
2
[Able to state an idea of hypothesis]
Sample answer:
Alkali metal have different reactivity.1
1 (c)
[No response given or wrong response] 0
Question Explanation Maximum
score
[Able to state the inference completely ]
Sample answer:
1. Lithium is the least reactive metal towards oxygen.
2. Lithium oxide is formed.
3
[Able to state the inference but not completely]
Any one inference
2
[Able to state an idea of inference]
Sample answer:
Reaction occurs1
1 (d)
[No response given or wrong response] 0
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Question Explanation Maximum
score
[Able to arrange the position of all metals in descending order of
reactivity correctly]
Sample answer:
Potassium/K, Sodium/Na, Lithium/Li
3
[Able to arrange the position of at least two metals in descending order of
reactivity correctly]
Sample answer:
Potassium/K, Sodium/Na // Sodium/Na, Lithium/Li
2
[Able to give an idea to arrange the metals]
Sample answer:
Lithium/Li, Sodium/Na, Potassium/K
1
1 (e)
[No response given or wrong response] 0
Question Explanation Maximum
score
[Able to predict the observation for the reaction between rubidium and
oxygen correctly ]
Sample answer:
Rubidium burns more vigorously and produces white fume.
3
[Able to predict the observation for the reaction between rubidium andoxygen ]
Sample answer:
Rubidium burns more vigorously.
2
[Able to state an idea to predict the observation for the reaction between
rubidium and oxygen correctly ]
Sample answer:
The reaction is more reactive.
1
1(f)
[No response given or wrong response] 0
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Question Explanation Maximum
score
[Able to record all the pH meter reading with one decimal place
accurately]:
Sample answer:
Set I : 13.2
Set II : 13.6
Set III : 13.3
3
[Able to record anytwo readings accurately]
Or[Able to record all the pH meter reading without one decimal place
correctly]
2
[Able to record anyone readings correctly] 1
1 (g)(i)
[No response given or wrong response] 0
Question Explanation Maximum
score
Able to construct a table to record the pH value for Set I, Set II and
Set III of experiment that contain :
1. Correct titles
2. pH values
Sample answer:
Set pH Value
I 13.2
II 13.6
III 13.3
3
Able to construct a table that contains the following:
1. Titles2. reading // ecf
2
Able to construct a table with at least one title/reading. 1
1(g)(ii)
[No response given or wrong response] 0
ttp //sp c e b ogspot co /
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Question Explanation Maximum
score
[Able to state the operational definition for alkali correctly]
Sample answer:pH value that is more than 7 when pH meter is dipped into a solution.
3
[Able to state the operational definition for alkali ]
Sample answer:
pH value that is more than 7.2
[Able to state an idea of operational definition for alkali ]
Sample answer:
pH value that is 13.1
1(g)(iii)
[No response given or wrong response] 0
Question Explanation Maximum
score
[Able to classify all the substances correctly]
Sample answer:
Strong alkali Weak alkali
Sodium hydroxide solution
Potassium hydroxide solution
Ammonia solution 3
[Able to classify anytwo substances correctly]2
[Able to classify anyone substance correctly] 1
1(g)(iv)
[No response given or wrong response] 0
p p g p
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KK051201-[To state problem statement]
Score Explanation/Rubric Maximum
score
2(a) Able to give the statement of problem by relating the following 4
information correctly:1. different metals
2. contact
3. electrolyte
4. rusting
Response is in question form:
Sample answer:
How do/(Do) different type of metals / (metals X and Y) in contact with
iron in the presence of an electrolyte affect rusting of iron ? // What is
the effect on the rusting of iron, when it is in contact with other metals
(metals X and Y) in the presence of an electrolyte?
3
Able to give the statement of problem.
Response is in question form:
Sample answer:
How do different type of metals / (metals X and Y) affect rusting?
2
Able to give an idea of statement of the problem.
Sample answer:
To investigate the effect of different type of metals on rusting//Does
electrolyte /X/Y/metal affect iron rusting?
1
No response or wrong response. 0
[KK051202-To state all variables]
Score Explanation/Rubric Maximum
score
2(b) Able to state all variables correctly:
Sample answer:
Manipulated variable: metal X and metal Y // stating 2 metals which one
metal is less electropositive and one metal is more electropositive than
iron.// pairs of X-Fe and Y-Fe
Responding variable: the rusting of iron // iron rusts or does not rust //
[any suitable observations: e.g. the formation of blue spot// the formation
3
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of pink colour // the formation of brown solid]
Fixed variable: iron nail// electrolyte/(named) // agar/jelly solution
//temperature
Able to stateany two variables correctly. 2
Able to stateany one variable correctly. 1
No response or wrong response. 0
[KK051202-To state a hypothesis]
Score Explanation/Rubric Maximum
score
2(c) Able to state the relationship between the manipulated variable and the
responding variable with direction correctly:
Sample answer:Metal Y causes iron nail rusting while metal X does not.// A moreelectropositive metal/(metal X) will prevent iron from rusting while a
less electropositive metal (metal Y) will be rusting iron.
3
Able to state the relationship between the manipulated variable and the
responding variable:
Sample answer:Metal Y speeds up iron nail rusting while metal X slows down rusting.
2
Able to state an idea of hypothesis:
Sample answer:
Metal X / Y affect the rusting of iron.
1
No response or wrong response. 0
[KK051203-list of materials and apparatus]
Score Explanation/Rubric Maximum
score
2(d) Able to give a complete list of materials and apparatus that involves thefollowing:
3
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1. iron nails
2. 1 metal above iron in electrochemical series
3. 1 metal below iron in electrochemical series
4. A suitable electrolyte, test-tubes, sand paper
Sample answer:Iron nails, magnesium/zinc/aluminium strip, tin/copper/lead/silver strip,
[agar-agar solution + potassium hexacyanoferrate(III)
solution+phenolphthalein indicator]/[any suitable electrolyte]/[water],
test-tubes/boiling-tubes, sand paper
Able to give a list of materials and apparatus that involves the following:
1. 1 metal above iron in electrochemical series
2. 1 metal below iron in electrochemical series
3. Any suitable electrolyte, any suitable container
2
Able to give a list of materials and apparatus that involves the following:
1. 1 metal above/below iron in electrochemical series// any suitable
electrolyte.
2. any container
1
No response or wrong response. 0
[KK051203-procedure of the experiment]
Score Explanation/Rubric Maximum
score
2(e) Able to state the following 6 steps:
1. [Clean the iron nails and metals strip with sand paper]2. [Coil iron nails with the metals]
3. [Place iron nails in separate container]
4. [Pour/add/fill the [named electrolyte] into the container]
5. [Leave them aside for several days]
6. [Record your observation]
Sample answer:
1. Clean iron nails, magnesium ribbon and copper strip with sand
paper.
2. Coil two iron nails tightly with magnesium ribbon and copper
strip.
3. Place all the iron nails in separate test tubes.
4. Pour the hot agar containing potassium hexacyanoferrate(III)
solution and phenolphthalein indicator into the test tubes.5. Keep the test tubes in a test tube rack and leave them aside for 3
days.
3
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6. Record your observations.
Steps 2,4,6 2
Step 2[coil iron nail with Mg/Cu], 4
1
No response or wrong response. 0
[KK051202-To make tabulation of data]
Score Explanation/Rubric Maximum
score
2(f) Able to exhibit the tabulation of data that includes the following four
information.
1. Heading for the manipulated variables Set//pair of metals
2. Examples of Sets//pair of metals I, II//Mg-Fe, Cu-Fe
3. Heading for responding variable observation
4.2x3 or 3x2 table
Sample answer:
Set//Pair of metals ObservationI//Mg-Fe
II//Cu-Fe
2
Able to exhibit the tabulation of data that includes the following two
information.
1. 1/3 from score 22. 2x2 table
Sample answer:
Set//Pair of metals Observation
1
No response or wrong response. 0
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END OF MARKING SCEME