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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

http://spmchem.blogspot.com/


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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

11



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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


10


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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


12


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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)



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)



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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)



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)



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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)



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)


ttp //sp c e b ogspot co /



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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)



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)


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

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


[KK051202-To state a hypothesis]


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


[KK051203-list of materials and apparatus]


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


[KK051203-procedure of the experiment]


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.

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6. Record your observations.

Steps 2,4,6 2

Step 2[coil iron nail with Mg/Cu], 4

1


[KK051202-To make tabulation of data]


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




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END OF MARKING SCEME

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