SULIT 4541/1/2/34541ChemistryMarking SchemeOctober2007

BAHAGIAN SEKOLAHKEMENTERIAN PELAJARAN MALAYSIA

______________________________________________PEPERIKSAAN SELARAS DIAGNOSTIK TINGKATAN 4 2007

FORM 4 CHEMISTRYMarking Scheme for Papers 1, 2 and 3

Peraturan pemarkahan ini mengandungi 23 halaman bercetak.

2

Paper 11 B 21 C 41 D2 A 22 D 42 B3 D 23 C 43 D4 C 24 D 44 C5 D 25 C 45 B6 A 26 C 46 D7 C 27 C 47 B8 C 28 C 48 B9 B 29 A 49 C

10 D 30 A 50 A

11 A 31 A12 A 32 C13 C 33 D14 B 34 C15 B 35 C16 D 36 D17 C 37 B18 C 38 C19 B 39 A20 C 40 A

Paper 2- Section A1. (a) P: 2.8Q: 2.7 R: 2.1 1

(b) (i) Group; 18, Period 2 1

(ii) Group ; 17, Period 2 1

(iii) Group: 1, Period 2 1

(c) (i) P 1

(ii) Has achieved a stable electron arrangement 1

(d) Q2 + H2O → HQ + HOQ 1

(e) R 1

(f) Q 1

(g) P < Q < R 1Total 10

2 a) 1. delivery tube is immersed in lime water 1

2. test-tube containing lime water is not stoppered 1

sample answer:

b) (i) CuCO3

(ii) copper(II) oxide

(iii) carbon dioxide

(iv) CuCO3 → Cu

3

1

r: formula 1

1

O + CO2 1

Lime water

4

c) (i) 11.89 – 11.45 = 0.44 g 1

(ii) 1. moles of gas = 0.44 / 0.01 144

2. Volume of gas = ( 0.01)(24) / 0.24 dm3 1

d) moles of XSO4 = Moles of XO

= 8.1 / 0.1 181

Total : 10

3 (a) (i) L+ 1(ii) E2- 1

(b) (i) 10 1(ii) 2.8 1

(c) M 1

(d) (ii) LJ r: JL, equation 1(ii) [can draw the diagram of electron arrangement correctly]

+

Ion L+ Ion J-

1.[all electrons and number of shells filled with electr2 [nucleus of atom labelled and charges of ion shown

(iii) In aqueous solution // molten stateIons can move freely//free to move

on correct]1correctly] 1

11

Total 10

5

4.(a) ( i ) Negatively charged ion // the ion that moves to theanode / electrode U / positive electrode 1

( ii ) Electrical Chemical 1

(b) ( i ) Cu²+ , H+ , Cl -- , OH -- 1

( ii )1+1

( iii ) A brown solid is deposited 1

( iv ) Blue to colourless / The blue colour of the solutionis decolourised./The intensity of blue colour decreases 1

(c) ( i ) Oxygen 1

( ii ) 1.Lower a glowing wooden splinter into the test tube. 1

2.The wooden splinter rekindles / relights. 1

10

5 (a)

b

c

d

( i ) water( ii ) methylbenzene// any organic solvent

ions

1.X ionises in water to produce hydrogen ions,2.Y has neutral molecules and cannot ionise

( i ) neutralization( ii ) 2HCl + Ba( OH )2 BaCl2+ 2H2O( iii ) 1.No. Of mole, HCl= 0.6 X 8.0 = 0.0048

----------1000

2. No. Of mole Ba(OH)2 = 0.0048/2 = 0.00243. Concentration of Ba(OH )2 = 0.0024 X 1000

-------------- //8

= 0.3

11

1

11

111

1

110

Electrode U Electrode T

Cl ─ , OH ─ Cu²+ , H+

6

6 (a) Pb2+, Al3+, Zn2+ {any two correct} 1+1

(b) 1.Lead(II) nitrate 12. Pb(NO3)2 1

(c) (i) Precipitation /Double decomposition 1(ii) Pb2+ + SO4

2─ → PbSO4 1

(d) 1. Add a few drops of potassium iodide solution 12. Yellow precipitate formed 1

(e) 1. Filter the mixture. 12.Dry the precipitate between sheets of filter paper. 1

Total 10

7

Section B7 (a)(i) Ionic 1

(ii) Covalent 1 2

(b) Between P and R

1. P atom has 2 valence electrons /electron arrangement of 2.8.2 1

2. Each P atom loses/donates/transfers 2 electrons to form P 2+ ion/

PP2+ + 2e- 1

3. R atom has 6 valence electrons 1

4. R atom gains/receives 2 electrons to form R 2─ ion /

R + 2e-R2─ 1

5. P and R achieve a stable electron arrangement 1

6. The two oppositely-charged ions are bonded together by a strong

electrostatic force ( to form an ionic bond) 1

[Diagram]

7. [all electrons and number of shells with electrons correct ] 1

8. [ nucleus of atoms lebelled and charges of ions shown correctly ] 1 8

2 2

P R

8

(ii) Between Q and R

1. Q atom has 4 valence electron and R atom has 6 valence electrons/electron

arrangement 1

2. Two atoms of element R will contribute 2 electrons each to one Q atom 1

3. for sharing so as to achieve a stable octet structure/stable electron arrangement

respectively// [diagram] 1

4. Therefore, they share two pairs of electrons to form a molecule with formula QR2

by (double) covalent bond 1 4

R Q R

(c) 1.Sodium chloride is an ionic compound (with Na+ and Cl – ions held in

fixed positions ) 1

2. Strong electrostatic force of attraction exists between cations and anions//

Na+ and Cl -//the oppositely-charged sodium ions and chloride ions

(or electrostatics forces of attraction) 1

3. A large amount of heat energy is required to overcome the strong forces

of attraction 1

4. Tetrachloromethane is a covalent compound (with simple molecules of CCl4) 1

5.The forces of attraction between molecules are weak//held together by weak

(Van der Waals) forces of attractions 1

6. A small amount of heat (energy) is needed to overcome the weak forces

between the molecules. 1 6

Total 20

x

x

xx

xx

xx

x

x

xx

xx

xx

9

8 ( a ) ( i ) Any suitable electrolyte. Example sodium chloride solution 1

( ii ) [Between P and Q]

. 1. Q is the negative terminal. So, P is below Q. 1

[Between Q and R]

2. R is the negative terminal. So, Q is below R. 1

[Between P and S]

3. S is the negative terminal So, P is below S. 1

4. But, the potential difference between P and S metalis the biggest. So, P and S are situated farthest apart. 1

5. S is the most electropositive metal while P is theleast electropositive metal. 1

6. Arrangement in descending order :

S, R, Q, P 1

(iii) 1. metal Q 12. Because metal Q is less electropositive than metal S 13. 0.6 V [value and unit correct] 1 10

10

8 ( b )

Iron spoonCopper metal

Copper(II) sulphate

[Diagram]1. Diagram complete and functional 12. Labels correct 1[Chemicals + Procedures]3. Iron spoon is used as the cathode/connected to the negative terminal of the dry

cell 14. Copper metal is used as the anode/connected to the positive terminal of the dry

cell 15. Copper ( II ) sulphate solution/any suitable copper salt solution is used as the

electrolyte 16. Turn on the switch./ circuit is completed 1[Observations]7. At anode : The size / mass of the copper metal decreases. 18. At cathode : The iron key is coated with a brown layer of metal 1[Chemical equations]9. At anode : Cu → Cu²+ + 2e- 110. At cathode : Cu²+ + 2e─ → Cu 1 10

20

11

SECTION C

9 (a)

(b)

1. Nitric acid is a strong acid and ethanoic acid is a weak acid2. Nitric acid ionises completey in water to produce high

concentration of hydrogen ions3. ethnoic acid ionises partially in water to produce low

concentration of hydrogen ions4. the higher the concentration of hidrogen ion the lower the pH

value.

Procedure – 3 marksIonic equation -1 markObservation – 1 markName of gas – 1 mark

Procedure1. Pour [2- 5 ]cm3 of acid solution into a test tube.2. Add zinc / magnesium powder into the test tube.3. Lower the burning wooden splinter into the test tube.4. equation :2H+ + Mg → Mg2+ + H2

5. Observation : Gas burns with a ‘pop’ sound6. Gas is Hydrogen

Or

1. Pour [2-5] cm3 of acid solution into the test tube.2. Add the calcium carbonate powder in the test tube.3. Pass through the gas liberated into lime water.4. equation :2H + + CaCO3 Ca 2+ + CO2 + H2O5. Observation : Lime water turns chalky/cloudy/milk6. Gas is carbon dioxide

1

1

1

1 4

111111

111111 6

12

(c)(i)

(ii)

● Solution with the exact concentration known.

1.Materials : solid sodium hydroxide , water.Apparatus : Electronic balance , beaker, 250cm3 volumetric flask,

glass rod.

●Calculation :2. No. Of moles of NaOH = 0.1( 250 ) = 0.025

-------------1000

3. Mass of NaOH = 0.025X 40g= 1.0g

Procedure :4. Weigh 1.0g of sodium hydroxide and dissolve it in 100 cm3

of distilled water in a beaker.5. Stir the solution using a glass rod.6. Pour the solution into the volumetric flask using a filter

funnel7. Rinse the beaker, filter funnel with distilled water and after

each rinse is transferred into the volumetric flask.8. Add distilled water drop by drop into the volumetric until

reaches the graduation mark.9. Stopper the volumetric flask and shake the volumetric flask

1

1

1

1

11

1

1

11 10

20

13

10 (a) (i) [Description of three complete reactions]eg. The reaction of magnesium with sulphuric acid toproduce magnesium sulphate and hydrogen.Suggested reactions:

Mg + H2SO4MgSO4 + H2

MgO + H2SO4MgSO4 + H2O

Mg(OH)2 + H2SO4MgSO4 + 2H2O

MgCO3 + H2SO4MgSO4 + H2O + CO2

1+1+1

(ii) 1.Pour 50 cm3 of 2 mol dm-3 sulphuric acid into a beaker.[Volume: 20 – 100 cm3, molarity: 0.5 – 2.0 mol dm-3]

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

suitable reactant mentioned above] into the acid.4.Stir the mixture evenly.5 Continue adding magnesium oxide [or any suitable

reactant] until some of it no longer dissolves.6.Filter to remove the excess magnesium oxide.7.Pour the filtrate into an evaporating dish and heat the salt

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

crystals.10.The crystals are pressed between a few pieces of filter

paper to be dried.

1

1

11

11

11

1

1 10

(b) (i) Ammonia gas 1 1

(ii)NH3 + H2O NH4

+ + OH- /

NH3 + H2O NH4OH

1 1

(iii) 1.Dip a glass rod into concentrated hydrochloric acid andthen bring it to the mouth of the test tube.

2.White fumes is formed.

1

1 2

(iv) 1. Blue precipitate is formed.2. Precipitate dissolves in excess ammonia3. A dark blue colouration/solution is formed.

111 3

TOTAL 20

END OF PAPER 2 MARKING SCHEME

14

Marking Scheme for Paper 3

1.(a) KK0501 – Making observations

Score Rubric

3

( Able to tabulate all the expected observations correctly )

Suggested answer :

Element Observations

P It burns slowly .White fume is formed

Q It burns rapidly . White fume is formed.

R It burns very rapidly and brightly . White fume is formed.

2( Able to state any two observations correctly )

1 ( Able to state any one observation correctly )

0 No response or wrong response

1 (b) KK0502 – Classifying

Score Rubric

3

( Able to arrange the metals in correct order )

Suggested answer :

R, Q, P

2

( Able to arrange at least R as the first metal )

Suggested answer :

R, P, Q

1

( Wrong order of arrangement )

Suggested answer :

P, Q, R

0 No response or wrong response

15

1 (c) KK054 – Making inference

Score Rubric

3

( Able to deduce the reactivity of metals based on the three observations )

Suggested answer :

Reactivity of R is the highest, followed by Q while P has the lowest reactivity

2

( Able to deduce reactivity of metals based on two observations )

Suggested answer :

Reactivity of R is the highest while reactivity of P is the lowest

1

( Able to deduce at least one observation correctly )

Suggested answer :

Reactivity of R is the highest / Reactivity of P is the lowest.

0 No response or wrong response

1 (d) KK0510 – Controlling variables

Score Rubric

3

( Able to state 3 correct and complete variables )

Suggested answer

Manipulated : Type of metals

Responding : Reactivity of metal with oxygen gas

Fixed : Size of metal

2( Able to state 2 correct and complete variables )

1 ( Able to give one correct and complete variable )

0 No response or wrong response

16

1 (e) KK0503 – Measuring And Using Number

Score Rubric

3

( Able to calculate the number of moles and concentration of solution

correctly )

Suggested answer :

2.3g of Q = 2.3 / 23 = 0.1 mol

250 cm³ of water = 250 / 1000 = 0.25 dm³

Concentration of solution = 0.1 / 0.25 = 0.4 mol dm-³

2

( Incorrect calculation )

Suggested answer :

2.3g of Q = 2.3 / 23 = 0.1 mol

Concentration of solution = 0.1 / 250 = 0.0004 mol dm³

1( At least the number of moles of Q is correct )

0No response or wrong response

17

2. (a) KK0505 – Predicting

Score Rubric

3 (Able to give correct answer and unit)

Suggested answer

2.27 V

2 (Able to give correct answer without unit)

Suggested answer :

2.27

1 (Round off to one decimal place)

Suggested answer :

2.2 V // 2.3 V

0 No response or wrong response

2. (b) KK06 – Communicating

Score Rubric

3 (Able to write overall equation correctly)

Suggested answer :

Zn + Cu 2+ → Cu + Zn 2+

2 (Able to write overall equation but incorrectly )

Suggested answer :

Zn + Cu +2 → Cu + Zn +2

1 (Able to give an idea to write overall equation)

Suggested answer :

Cu + Zn 2+ → Zn + Cu 2+

0 No response or wrong response

18

2. (c) KK07 – Using Space Time-Relationship

Score Rubric

3 (Able to give the answer correctly)

Suggested answer :

The mass will decrease

2 (Able to give the answer but incorrectly)

Suggested answer :

Zinc electrode becomes thinner//dissolves in the solution

1 (Able to give an idea)

Suggested answer :

Zinc electrode corrodes

0 No response or wrong response

2. (d) KK08 – Interpreting data

Score Rubric

3 (Able to arrange the five metal in ascending order)

Suggested answer :// symbol

Copper, lead, iron, zinc, magnesium // Cu, Pb, Fe, Zn, Mg

2 (Able to arrange at least three metal in ascending order)

Suggested answer :

Zinc, Magnesium, Copper, lead, iron, // Zn, Mg, Cu, Pb, Fe,

1 (Able to arrange the five metal but in descending order)

Suggested answer :

Magnesium, zinc, iron, lead and copper // Mg, Zn, Fe, Pb, Cu

0 No response or wrong response

19

2. (e) KK0502 –Classifying

Score Rubric

3 (Able to classify all ions into positive ions and negative ions correctly)

Suggested answer :

Positive ions: Cu2+, H+

Negative ions: SO42─, OH─

2 (Able to classify one positive ion and one negative ion for copper(II)

sulphate.

Suggested answer :

Positive ions: Cu2+

Negative ions: SO42─

1 (Able to give any one ion correctly)

Suggested answer :

Positive ions: Cu2+ / H+ or

Negative ions: SO42─ / OH─

0 No response or wrong response

2. (f) KK11 – Making hypothesis

Score Rubric

3 (Able to give complete answer correctly)

Suggested answer :

The further the distance between the metals at the negative electrode, the

bigger the voltage reading

2 (Able to give incomplete answer)

Suggested answer :

The further the distance between the metals, the bigger the voltage

reading

1 (Able to give an idea)

Suggested answer :

Different pair of metals, have different voltage reading

0 No response or wrong response

20

3 (a) KK051201 - Problem statement

Score Rubric

3

( Able to state the problem statement clearly and accurately)

Suggested answer :

How to determine whether a given sample of acetamide is pure or not?

2

(Able to state the problem statement slightly inaccurate)

Suggested answer :

Which acetamide is pure?

1

(Able to provide an idea of a problem statement)

Suggested answer :

To study the purity of acetamide.

0 No response or wrong response

3 (b) KK051202 – Stating all variables

Score Rubric

3

(Able to state all the corresponding variables accurately)

Suggested answer

Manipulated variable : Acetamide A and acetamide B// Type of Acetamide

Responding variable : melting point

Fixed variables : quantity/mass of acetamide

2 (Able to state two corresponding variables accurately)

1 [Able to state any one corresponding variable correctly].

0 No response or wrong response

21

3(c) KK0511- Making hypothesis

Score Rubric

3

(Able to state the hypothesis correctly)

Suggested answer

Pure acetamide has a melting point of 83oC [whereas impure acetamide

has no fixed melting point].

2

(Able to state the hypothesis slightly inaccurate)

Suggested answer

The melting point of acetamide A and B is different.

1

(Able to provide an idea of hypothesis)

Suggested answer

The melting point of acetamide A is lower/ higher than B.

0 No response or wrong response

3 (d) KK051205 – List of materials and apparatus

Score Rubric

3

(Able to list all materials and apparatus correctly)

Suggested answer

Materials: Acetamide A, acetamide B, water

Apparatus: Boiling tube, beaker, thermometer, tripod stand, retort stand

and clamp, Bunsen burner, stop watch, wire gauze, spatula

2

(Able to list the basic materials and apparatus required)

Suggested answer

Materials: Acetamide A, acetamide B

Apparatus: Boiling tube , beaker, thermometer, stop watch

1

(Able to provide an idea of materials and apparatus used)

Suggested answer

Materials: Acetamide Apparatus: [state at least one apparatus]

0 No response or wrong response

22

3(e) KK051204 – Experimental procedure

Score Rubric

3

[Able to state all experimental steps correctly]

Suggested answer

1. Fill a boiling tube with solid acetamide A until one third full.

2. Suspend the boiling tube in a beaker half filled with water.

3. Heat the water until the temperature of acetamide A reaches about 60oC.

[50 – 60oC]

4. Stir slowly with the thermometer,

5. Record the temperature of acetamide at half minute intervals until the

temperature reaches 90oC. [90 – 100oC]

6. Repeat steps 1 to 5 by replacing acetamide A with acetamide B.

7. Plot graphs of Temperature against time for both substances to determine

the melting point.

2[Able to provide 4 steps correctly to carry out the experiment]

1[Able to provide minimum of 2 steps correctly to carry out the experiment]

0 No response or wrong response

23

3 (f) KK 0501-05 – Tabulation of data

Score Rubric

3

(Able to construct a table correctly containing the following elements)

Substance, time, temperature

Suggested answer

Acetamide A Acetamide B

Time

(min)

Temperature(oC)

Time

(min)

Temperature(oC)

2

(Able to construct a tabulation of data containing the following elements)

Subtance, melting point

Suggested answer

Acetamide Melting point (oC)

A

B

1 (An idea of a tabulation of data )

- Minimum of 2 rows and columns

0 No response or wrong response

Total marks for question 3 : 18

Maximum marks: 17

END OF MARKING SCHEME FOR PAPER 3.