perfect score chemistry sbp 2012 - answer

1

BAHAGIAN PENGURUSAN

SEKOLAH BERASRAMA PENUH DAN SEKOLAH KLUSTER

JAWAPAN

MODUL PERFECT SCORE

2012

CHEMISTRY

[KIMIA]

Set 1 Set 2 Set 3 Set 4 Set 5

2

JAWAPAN SET 1

PAPER 2 : STRUCTURED QUESTION

SECTION A

No Explanation Sub Mark Total Mark

1(a)(i) The number of proton in the nuclues of an atom 1 1

(ii) 18 1 1

(b) M and N,

because both atoms have same proton number but

different nucleon number/ the same the number of

proton but different the number of neutron

1

1

2

(c)(i) 2.8.6 1 1

(ii) Group 16 , Period 3 1 1

(iii) 6 valence electron ,

three shells fill / occupied with electron

1

1

2

(d) M-

1 1

Total 9

No Explanation Sub Mark Total Mark

2(a) 2.8.3 1 1

(b)(i) Z 1 1

(ii) Z atom has achieve a stable octet electron arrangement.

Atom does not donate or receive / share electron with

other atom.

1

1

2

(c)(i) VW

1 1

(ii) Draw

+ -

1. Correct number of shell and eletron for ion V and ion W 2. Correct charge of ion V and ion W

1

1

2

(d)(i) W / Y 1 1

(ii) U 1 1

(iii) T 1 1

Total 10

W V

3

No Explanation Sub Mark Total Mark

3(a)(i) 2.8.6 1 1

(ii) 16 1 1

(b)(i) Atomic size decrease / become smaller 1 1

(ii) The number of proton increase/ positive charge increase

Force of attraction between neucleus and valence

electron increase

1

1

2

(c) Has achieve a stable octet electron arrangement

Atom does not donate, receive or share electron with

other atom.

1

1

2

(d) Al / Aluminium 1 1

(e) 2Na + 2H2O 2NaOH + H2

Correct the formula reactant and product

Balance equation

1

1

2

Total 10

No Explanation Sub Mark Total Mark

4(a) K

J/ L / M

1

1

2

(b)(i) J/L/M 1 1

(ii) Atom of J/L/M is not stable// has 1/6/ 7 valence

electron

2 atoms of J/L/M share a pair of electron

To achieve duplet/octet electron arrangement

1

1

1

3

(c)(i) 17 1 1

(ii) 17, atom has 7 valence electron 1 1

(d) M,L, K 1 1

(e) K+ 1 1

(f) KM 1 1

Total 11

No Explanation Sub Mark Total Mark

5(a)(i) Magnesium / Mg 1 1

(ii) Mg2+ 1 1

(iii) Chlorine / Cl2 1 1

(iv) gas 1 1

(v) has free moving ions 1 1

(b)(i) covalent compound 1 1

(ii) T2 oC 1 1

(iii) becomes slower 1 1

(iv)

1 1

Total 9

4

No Explanation Sub Mark Total Mark

6(a)(i) 0.125 mol 0.125x 6.02 x 10

23 // 1.7525 x 10

23 molecules

1 1

3

(ii) 0.125 x 44 = 5.5 g 1 (b)(i) Chemical formula that shows simplest ratio of atoms of

elements/each element in a compound 1 7

(ii) Mg = 2.4g , O = 1.6g 1+1 (iii) 1 : 1 1 (iv) MgO 1 (v) To allow oxygen enter the crucible 1 (vi) Copper is less reactive towards oxygen than hydrogen 1

Total 10

No Explanation Sub Mark

Total Mark

7(a) Chemical formula that shows actual number of atoms of elements/each element in a molecule

1 1

(b) Number of mole 1 1 (c)(i) Method 1 1 3 (ii) Magnesium is reactive //Magnesium reacts easily with

oxygen 1

(iii) To allow oxygen/air to enter the crucible//To ensure magnesium reacts completely

1

(d)(i) Mass of Pb = 49.68 g 1 5 (ii) No.of mole of Pb = 0.24 mol 1 (iii) Mass of oxygen = 3.84 g 1 (iv) No. of mole of O = 0.24 mol 1 (v) Empirical formula = PbO 1

Total 10

No Explanation Sub Mark

Total Mark

8(a)(i) Chemical formula that shows the simplest ratio of atoms of each element in the compound

1 2

(ii) To dry hydrogen gas//To absorb water/moisture 1 (b)(i) Copper = 8.00g

Oxygen = 2.00g 1 1

4

(ii) 8/64 : 2/16 = 1:1 1 (iii) CuO 1 (c)(i) To avoid the oxidation of copper//To avoid the formation of

copper oxide 1 2

(ii) Repeat the process of heating, cooling and weighing until the mass of copper is constant/no change

1

(d)(i) Magnesium is more reactive towards oxygen than hydrogen//Magnesium is placed above hydrogen in the

reactivity series

1 2

(ii) Iron oxide/Tin oxide/Lead oxide/Silver oxide 1

Total 10

5

SECTION B

No Rubric Sub Mark Marks

9(a) 1.Number of proton for both isotopes is 6

2.Number of electron for both isotopes is 6

3.Nucleon number for first isotope is 12

4.Nucleon number for second isotope is 14

5.Both isotope has different physical properties

6.Both isotope has same chemical properties

1

1

1

1

1

1

6

(b) (i) Naphthalene / acetamide 1

(ii) 1. Water 2. Melting point of X below than boiling point of

water / uniform heating

1

1

2

(iii) From 0 to t1 minutes

1. In solid state 2. Particles are closely packed and in orderly

arrangement

3. Kinetic energy of particles very low 4. Attraction force between particles very strong

From t1 to t2 minutes

1. In solid and liquid state 2. Some particle are closely packed and in orderly

manner and some particle are slightly lose packed

and in orderly manner

3. Kinetic energy of particles constant

From t2 to t3 minutes

1. In liquid state 2. Particles are closely packed and in orderly manner 3. Attraction forces between particles become weaker

1

1

1

1

1

1

1

1

1

1

Max 9

(v) 1. correct curve

2. Label freezing point ( 80 o C )

Sample answer

1

1

2

TOTAL 20

Temperature (oC)

Time (min)

80 oC

6

No Explanation Sub Mark Total Mark

10 (a) Electron arrangement of helium atom is 2 // Helium atom has two valence electrons. Achieved a duplet electron arrangement. Helium atom will not gain, lose or share electrons with other

atoms.

Electron arrangement of chlorine atom is 2.8.7 // Chlorine

atom has seven valence electrons. Chlorine atom needs one electron to achieve the octet

electron arrangement. Thus, two chlorine atoms share one pair of electrons.

1 1 1

1

1

1

6

(b)(i)

Covalent compound

1

1 + 1

3

(b)(ii) Electron arrangement of magnesium atom is 2.8.2 Magnesium atom donate 2 electrons to achieve the stable

octet electron arrangement A positive ion / magnesium ion / Mg

2+ ion is formed //

Mg Mg2+ + 2e // [Diagram] Electron arrangement of chlorine atom 2.8.7 chlorine atom accepts 1 electron to achieve the stable octet

electron arrangement A negative ion / chloride ion / Cl

ion is formed //

Cl2 + 2e 2Cl

// [Diagram]

Mg2+

and Cl ions are attracted to each other by a strong

electrostatic/ionic force.

1

1

1

1

1

1

1

7

(c) Naphthalene cannot conduct electricity/non-electrolyte. Naphthalene does not has ions // exist as molecule. Sodium chloride solution conduct electricity/ an electrolyte. In sodium chloride solution, sodium ions/Na

+ and chloride

ions/ Cl are free to move.

1 1 1

1

4

Total 20

C Cl Cl

Cl

Cl

7

No Explanation Sub Mark Total Mark

11(a)(i) Al3+ , Pb4+ 1+ 1 4 (ii) Aluminium oxide

Lead(IV) oxide 1 + 1

(b)(i) (CH2O)n = 60 12n + 2n + 16n = 60 n = 2 Molecular formula = C2H4O2//CH3COOH

1

1 1

3

(ii) CaCO3 + 2CH3COOH (CH3COO)2Ca + H2O + CO2

2 2

(c)(i) 1.Green solid turn Black 2. Lime water becomes cloudy

1 1

2

(ii) CaCO3 CaO + CO2 1 + 1 2 (iii) 1. mol of calcium carbonate decomposed into 1 mol of

calcium oxide and 1 mol of carbon dioxide 2. Calcium carbonate is in solid state, calcium oxide is in

solid state and carbon dioxide is in gaseous state

1

1

2

(iv) 1. No. of mole for CuCO3 = 12.4 / 124 = 0.1 mol

2. 1 mol of CuCO3 produces 1 mol of CuO

Therefor No. of mole for CuO = 0.1 mol

3. Mass of CuO = 0.1 X 80 g = 8 g

1 1

1

3

(v) Mass of oxygen is 0.8g

Simplest mol ratio : Cu : O = 3.2/64 : 0.8/16 = 1 : 1

1 1

2

Total 20

8

No Explanation Sub Mark Total Mark

12(a)(i) Cation Anion

1 1

5

(ii) Iron(III) ion and chloride ion 1 + 1 (iii) K2SO4 1 (b)(i) Lead(II) sulphate

Pb(NO3)2 + K2SO4 PbSO4 + 2KNO3 1

1 + 1 8

(ii) 1 mol of lead(II) nitrate reacts with 1mol of potassium sulphate producing 1 mol of lead(II) sulphate and 2 mol of potassium

nitrate.

1

(iii) 1.No.of mol of K2SO4 = 10 x 0.5 = 0.005 mol 1000 2. 1 mol of K2SO4 producing 1 mol of PbSO4 No of mol PbSO4 = 0.005 mol 3. Mass of PbSO4 = 0.005 x 303