2010 skema pat sbp

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CHEMISTRY

MARKING SCHEME

PAPER 1PAPER 2

PAPER 3

Peraturan Pemarkahan

4541

Chemistry

Oktober

2010

BAHAGIAN PENGURUSAN

SEKOLAH BERASRAMA PENUH DAN SEKOLAH KECEMERLANGAN

KEMENTERIAN PELAJARAN MALAYSIA

PEPERIKSAAN SELARAS AKHIR TAHUN

TINGKATAN 4 TAHUN 2010

Kertas soalan ini mengandungi 16halaman bercetak

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SULIT Peperiksaan Selaras Akhir Tahun Tingkatan 4

4541 2010 Hak Cipta Sekolah Berasrama Penuh

SULIT

Paper 1

1 A 21 B 41 D

2 B 22 C 42 D3 A 23 A 43 A

4 D 24 B 44 A

5 B 25 B 45 D

6 D 26 C 46 A

7 B 27 A 47 B

8 A 28 D 48 B

9 D 29 C 49 A

10 B 30 D 50 D

11 C 31 B

12 A 32 C13 B 33 B

14 C 34 A

15 D 35 C

16 C 36 A

17 A 37 A

18 C 38 B

19 B 39 D

20 D 40 A

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SULIT

Paper 2

1 Rubric Score

(a) (i) 19 1

(ii) 18 1

(iii) 2.8.7 1

(iv) V and X

Both atoms V and X have the same proton number but different nucleon number

1

1

(b) (i)

R S

1 + 1

(ii) [mark freezing point on the graph & label]

Heat released to the surrounding is equal to the

Heat released as the particles attract one another to form a solid

1

1

1

10

Temperature (oC)

Time(s)

t1 t2

Freezing point

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SULIT

2 Rubric Score

(a) Period 3; Group 13 1 + 1

(b) Atom W has stable octet electron arrangement 1

(c) (i) S 1(ii) [state either onespecial characteristics of transition elements]

Show different oxidation number Formed colour ions or compounds. Are useful catalysts Formed complex ion

1

(d) V, U, P 1

(e) (i) R 1

(ii) R has bigger atomic size than Q//the valence electron is further away from

nucleus R than Q

Nuclei attraction of R towards valence electron is weaker than Q//Atom R iseasier to donate its valence electron

1

1

(f) [mark correct position of element M]

P U M V

Q T W

R S

1

10

3 Rubric Score

(a) (i) Anion is negatively-charged ion 1

(ii) Cl-, OH- 1

(b) Electricity energychemical energy 1

(c) (i) X 1

(ii) 2H++ 2e-H2 1

(iii) Bring a lighted wooden splinter to the mouth of the test tube Popsound is heard 11

(d) (i) iodine 1

(ii) Concentration of I-is higher than OH-

I-is selectively discharged to produce iodine

1

1

10

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SULIT

4 Rubric Score

(a) (i) Blue to red 1

(ii) H+ 1

(b) No

No presence of H+ion//ethanoic acid exist as a neutral molecule

1

1

(c) Ethanoic acid has higher pH value than hydrochloric acid

Ethanoic acid is weak acid and hydrochloric acid is strong acid//ethanoic acid ionises

partially in water and hydrochloric acid ionises completely in water

Concentration of H+in ethanoic acid is lower than hydrochloric acid

1

1

1

(d) (i) Effervescence occurs//bubbles of colourless gas is released. 1

(ii) [correct formula of reactant & product]

[balanced chemical equation]

CaCO3+ 2 HClCaCl2+ CO2+ H2O

1

1

10

5 Rubric Score

(a) (i) neutralisation 1

(ii) Pink to colourless 1

(ii) Number of moles of NaOH =

Number of moles of HCl = 0.005

Molarity of HCl =

or

1

1

or

1

1(b) (i) [correct formula of reactant & product]


Pb(NO3)2 + 2KClPbCl2+ 2KNO3

1

1

(ii) Filter the mixture 1

(iii) Number of moles of lead nitrate =

1

(iv) 1 mol of lead nitrate produce 1 mol of PbCl2

0.01 mol of lead nitrate produce 0.01 mol of PbCl2

Mass of precipitate =

1

1

10

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SULIT

6 Rubric Score

(a) (i) Contact process 1

(ii) [state any two materials]

Sulphur, air, water

1 + 1

(iii) Gas dissolved in rain water

To form acid rain

1

1

(b) (i) [correct formula of reactant & product]


N2+ 3 H2 3NH3

1

1

(ii) iron 1

( c) (i) Ammonium sulphate 1

(ii) [state any one use of sulphuric acid]

as electrolyte in lead-acid accumulator

manufacture of detergent/paint

1

10

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SULIT

7 Rubric Score

(a) Electron arrangement of R : 2.8.7Electron arrangement of Q : 2.8.8.2Atom Q has 2 valence electrons and 3 shells occupied with electrons.Q is located in Group 2 and Period 4.

1

1

1+ 1

1+ 1

61. Atom Q losses 2 electron2. to achieve the stable octet electron arrangement3. Q2+ion is formed4. Two atoms R, each receives 1 electron from atom Q to achieve the stable octet electron

arrangement

5. Two Rions are formed.6. An ion Q2+and two ion R-are attracted together by strong electrostatic forces7. A compound with formula, QR2is formed.

1

1

1

1

1

1

1

7

(c) CR4

[sharing 4 pairs of electron between C atom and R atom][electron arrangement of all atoms]

1

1

1

3

Melting pointCompound (b) has high melting point

compound (c) has low melting point.

Electrical conductivityCompound (b) can conduct electricity in liquid or aqueous solution state.Compound (c) can not conduct electricity in any state.

1

1

1

1

4

20

C

R

R

R

R

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8 Rubric Score

(a) (i) Pass dry hydrogen gas to remove the air in the combustion tube before heating lead

oxide.

To avoid explosion.

1

1

2(ii) [correct formula of reactant & product]


PbO + H2Pb + H2O

1

1

2

(b) [Procedure]

1. Clean magnesium ribbon with sand paper2. Weigh crucible and its lid3. Put magnesium ribbon into the crucible and weigh the crucible with its lid4. Heat strongly the crucible without its lid5. Cover the crucible when the magnesium starts to burn and lift/raise the lid a little at

intervals6. Remove the lid when the magnesium burnt completely7. Heat strongly the crucible for a few minutes8. Cool and weigh the crucible with its lid and the content9. Repeat the processes of heating, cooling and weighing until a constant mass is

obtained

Results:

Mass/g

Crucible + lid xCrucible + lid + magnesium y

Crucible + lid + magnesium oxide z

Calculations

Empirical formula: MgaOb/ MgO

Element Mg O

Mass (g) y-x z-y

Number of moles24

xy

16

yz

Simplest ratio of moles a b

1

1

1

1

1

1

1

Max:7

1

1

1

111

(c) Both empirical formula and molecular formula shows glucose is made up of carbon and

hydrogen

empirical formula tell the simplest ratio of carbon atom to hydrogen atoms,

= 1: 2 : 1

Molecular formula shows the actual number of carbon atoms and hydrogen atoms in its

molecule.

Each glucose molecule consist of 6 carbon atoms, 12 hydrogen atoms and 6 oxygen

atom

1

1

1

1

1

5

20

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9 Rubric Score

(a) Salt is an ionic compound

where hydrogen ion from the acid is replaced by metal ions/ammonium ion.

1

1

2

(b) (i) Soluble salts : zinc sulphate, copper (II) sulphateInsoluble salts: lead(II) sulphate, calcium sulphate

1 + 11+ 1

4

(ii) Sulphuric acid

Zinc/zinc oxide/zinc carbonate or

copper(II) oxide/copper(II) carbonate

1

1

2

(c) 1. Pour 50 cm of 2 mol dm- sulphuric acid into a beaker.[Volume: 20 100 cm

3, molarity: 0.5 2.0 mol dm-3]

2. Warm the acid.3. Use a spatula to add copper oxide/zinc oxide powder [or any

suitable reactant] into the acid.

4. Stir the mixture evenly.5. Continue adding copper oxide [or any suitable

reactant] until some of it no longer dissolves.

6. Filter to remove the excess copper oxide[or any suitablereactant].

7. Pour the filtrate into an evaporating dish and heat the saltsolution to produce a saturated solution.

8. Cool the saturated solution until crystals are formed.9. The content are filtered to obtain the sulphate

crystals.

10.The crystals are dried by pressing between filter paperspaper

11.Correct formula of reactant & product12.Balanced chemical equation.

1

1

1

1

1

1

1

1

1

1

1

1

12

20

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10 Rubric Score

(a) [functional diagram]

[label iron key as the cathode]

[label suitable metal as the anode]

[label suitable electrolyte]

Example:

1

1

1

1

4

(b) (i) Q : Copper

Copper is more electropositive than silver

Copper can displace silver from silver nitrate solution

Produce silver

Copper(II) ion

1

1

1

1

1

5

(ii) P, Q/Cu, Ag 1

1

(c) R : zinc/any metal which is more electropositive than copper

Negative terminal : zinc

Positive terminal : copperZinc ionises/release electrons

Electrons flow from negative terminal to positive terminal through external circuit

Copper(II) ion is discharged at postitive terminal

Half equation:

Negative terminal : ZnZn2++ 2e-

Positive terminal : Cu2++ 2e-Cu

Observation:

Negative terminal: zinc become smaller

Positive terminal: copper become bigger/brown solid deposited

1

1

11

1

1

1

1

1

1

10

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SULIT

Paper 3

Question 1(a)

Rubric Score

Able to record the observation correctly.

Sample answer:

Potassium burns more vigorously and produces white fumes.

3

Able to record the observation less correctly.

Sample answer:

Potassium burns vigorously and produces white fumes.

2

Able to state an idea of the observation.

Sample answer

Potassium burns in oxygen/produces white fumes.

1

No response or wrong response 0

Question 1(b)

Rubric Score

Able to state the three variables and controlling the three variables correctly

Sample answer:

Variable Action to be taken

(i) Manipulated VariableType of alkalimetals//lithium, sodium,

potassium

(i) Method to manipulate the variableReplace lithium with sodium and potassium

(ii) Responding Variable

Reactivity towards

oxygen

(ii) What to observe in the responding variableBurning of alkali metals in oxygen gas

(iii) Fixed Variable:

Size of alkali metals

(iii)Method to maintain the fixed variableRepeat the experiment with the same size of

alkali metals

6

Able to give any 5 statements correctly 5






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SULIT

Question 1(c)

Rubric Score

Able to state the hypothesis accurately

Sample answer:

The lower position of alkali metals in Group 1, the more reactive the metals towardsoxygen

3

Able to record the hypothesis less correctly.

Sample answer:

Reactivity towards oxygen increases when going down Group 1 Potassium is more reactive than sodium and lithium towards oxygen.

2

Able to state an idea of hypothesis.

Sample answer

Metals burns in oxygen.

1


Question 1(d)

Rubric Score

Able to state two inferences accurately

Sample answer:

Sodium react with oxygen Produce sodium oxide

3

Able to state at least one inference.

Sample answer:

Sodium burns in oxygen form sodium oxide

2

Able to state an idea of inference.

Sample answer

Reaction occurs

1


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Question 1(e)

Rubric Score

Able to state operational definition accurately

Sample answer:

The burning of metals when is alkali metals is burnt in oxygen gas

3

Able to state operational definition less accurately

Sample answer:

Burning of metals in oxygen gas

2

Able to state an idea of operational definition.

Sample answer

Reaction with oxygen gas

1


Question 2(a)

Rubric Score

[Able to write all the volumes with units accurately]

Initial burette readings: 0.80 cm3, 13.40 cm3, 25.90 cm3

Final burette readings : 13.40 cm3, 25.90 cm3, 38.40 cm3

3

[Able to record all the volumes accurately but without units one decimal place]

Initial burette readings: 0.8, 13.4, 25.9

Final burette readings : 13.4, 25.9, 38.4

2

[Able to write at least four readings of the volumes accurately] 1


Question 2(b)

Rubric Score

[Able to construct a table correctly containing three labeled columns with correct

units and record all the burette readings and volume of acids used accurately ]

Suggested answer:Titration No. I II II

Initial burette

reading/cm3

0.80 13.40 25.90

Final burette

reading/cm3

13.40 25.90 38.40

Volume of acid

used/cm3

12.60 12.50 12.50

3

[Able to construct a table correctly containing three labeled columns without

units/one decimal place and record all the volumes accurately]

2

[Able to construct a table with at least three labels and four correct readings] 1

No response given / wrong response 0

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Question 2(c)

Rubric Score

[Able to calculate the average volume of acid used correctly and with unit]

Suggested answer:

Volume of acid used = 12.60 + 12.50 + 12.503

= 12.53 cm3

3

[Able to calculate the average volume correctly but without unit.] 2

[Able to show the calculation of average volume of acid used but incorrect answer] 1


Question 2(d)

Rubric Score

[Able to state the volume correctly]

6.25 cm3

3

[Able to state the volume but to one decimal place]

6.3 cm3// [6.0 7.0] cm3

2

[Able to state the volume but inaccurately]

12.5 cm3//25.0 cm3

1


Question 2(e)

Rubric Score

[Able to classify the strong acids and the weak acids into their group the correctly]

Strong acids: hydrochloric acid, sulphuric acid, nitric acid

Weak acids: ethanoic acid, carbonic acid

3

[Able to calssify at least three acids correctly]

Strong acids: ethanoic acid, carbonic acid

Weak acids: hydrochloric acid, sulphuric acid, nitric acid

2

[Able to classify at least any two acids correctly] 1


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Question 3(a)

Rubric Score

[Able to state the problem statement accurately]

Sample answer:How does the distance between two metals in the electrochemical series affect the

voltmeter reading in a voltaic cell?

3

[Able to state the problem statement accurately]

Sample answer:

How does the position of metals in the electrochemical series affect volmeterreading?

To construct electrochemical series bases on the volmeter reading in a voltaic cell

2

[able to show an idea of problem statement]

Sample answer

How does pairs of metals affect volmeter reading?

1


Question 3(b)

Rubric Score

[Able to state three variables accurately]

Sample answer:

Manipulated variables: pairs of metalsResponding variables : voltmeter reading

Fixed variable: type of electrolyte

3

[Able to state two variables accurately] 2

[Able to state one variable] 1


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SULIT

Question 3(c)

Rubric Score

[Able to state the relationship between manipulated variable and responding

accurately]

Sample answer:

The further the two metals in the electrochemical series, the higher the voltmeterreading

The distance between two metals in electrochemical series become greater, thegreater the voltmeter reading

3

[Able to state hypothesis less accurately]

Sample answer:

The higher the voltmeter reading, the further the two metals in theelectrochemical series

2

[Able to show an idea of hypothesis]

Sample answer:

The metals affect the voltmeter reading

1


Question 3(d)

Rubric Score[Able to state materials & apparatus accurately]

Suggested answer:

Materials : copper strips, P, Q and R strips; copper(II) sulphate solution[any suitable

electrolyte]

Apparatus : voltmeter, beaker, sand paper and connecting wires

3

[Able to state materials & apparatus less accurately]

Sample answer:Materials : copper, P, Q, R; copper(II) sulphate solution

Apparatus : voltmeter, beaker

2

[Able to show an idea of materials and apparatus]

Sample answer:

Materials : copper, P/Q/R; copper(II) sulphate solution

Apparatus : voltmeter

1


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Question 3(e)

Rubric Score

[Able to state the procedures accurately]

Suggested answer:1. A beaker is filled with copper (II) sulphate solution.

2. The copper and P strips are cleaned with sand paper.

3. The strips are immersed into the solution and connected by wires

to a voltmeter.

4. The reading of the voltmeter is recorded.

5. Steps 1 - 4 are repeated with replacing P with Q and R.

3

[Able to state the procedure less accurately]

Sample answer:

1. The metal strips are immersed into the solution and connected by wires to avoltmeter.

2. The reading of the voltmeter is recorded.3. Steps 1 - 4 are repeated with replacing P with Q and R.

2

[Able to show an idea of procedures]

Sample answer:

1. The metals immersed into the solution2. The reading of the voltmeter is recorded.

1


Question 3(f)

Rubric Score

[Able to show construct table with correct heading and units and state all the pairs of

metals]

Suggested answer:Pair of metals Volmeter reading/V

P - Cu

Q - CuR - Cu

.

2

[Able to show construct table with heading and without units]

Sample answer:Pair of metals Volmeter reading

1

No response or wrong response 0End of Answer Scheme

2010 skema pat sbp

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