[done edu.joshuatly.com] kedah stpm trial 2010 chemistry [w ans] [33e48b52]

8/13/2019 [Done Edu.joshuatly.com] Kedah STPM Trial 2010 Chemistry [w Ans] [33E48B52]

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CONFIDENTIAL*/SULIT*

[Turn over(Lihat sebelah)

SULIT *

Jawapan Peperiksaan Percubaan STPM 2010

Kimia Kertas 1

1 D 11 B 21 D 31 D 41 D

2 A 12 A 22 D 32 C 42 B

3 A 13 C 23 D 33 B 43 C

4 C 14 C 24 C 34 B 44 B

5 B 15 D 25 B 35 B 45 A

6 A 16 D 26 A 36 B 46 B

7 D 17 D 27 C 37 D 47 A

8 D 18 A 28 C 38 A 48 D

9 C 19 C 29 B 39 B 49 B

10 B 20 B 30 C 40 B 50 B

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CONFIDENTIAL*/SULIT*

Paper 2 Answer Chemistry STPM Trial 2010

Section A

1 (a) (i) 1

(ii) 1 Bent / V-shape

(iii) 1 Right shape of sp3orbitals1 Label sp

3hybrid orbital of S atom and 1s orbital of H atom

(b) (i) 1 O is more electronegative than S /

Bonding pair electrons in the OH bond are drawn closer to the O atom compared to the

bonding pair electrons in the SH bond.

1 Repulsion between bonding pair electronbonding pair electrons in H2O in H2S1 bond angle H-O-H > bond angle H-S-H

(ii) 1 van der Waals forces between H2S molecules

1 Hydrogen bonds between H2O molecules

1 Hydrogen bonds are stronger than van der Waals forces

2 (a) (i) 1 pH is the measure of hydrogen ion concentration // pH = - log [H+]

(ii) pH = - log [H+] ; 3.5 = - log [H

+]

1 [H+] = 3.16 x 10

-4mol dm

-3

(b) (i) HX + NaOHNaX + H2O

111

10.05.270.25 x

Mx

1 M = 0.11 mol dm-3

(ii) 1 Orange juice is a weak acid. // Orange juice dissociates partially.

1 The concentration of the H+released is not the same as the concentration of the acid in the orange

juice.

(iii) 1 cK]H[ a

111.0

)10x16.3(

c

]H[K

242

a

= 9.1 x 1O-7

mol dm-3

(iv) 1 Orange juice is a weak acid (pH = 3.5) and NaOH is a strong base, the pHrange of phenolphthalein will enable it to produce a sharp end point.

1 Colour change is more prominent from colourless to pink

3 (a) (i) 1 Ge4+

>Sn4+

>Pb4+

(ii) 1 Ge2+

(iii) 1 Pb2+

1 The electrode potential for Pb4+

/Pb2+

is positive, this shows that Pb4+

is readily converted to Pb2+

.

(b) (i) 1 SiO2 / silica / silicon dioxide

(ii) 1 Telecommunication / endoscope.

(iii) 1 Optical fibres can transmit more information than copper wires.

1 Optical fibres have 100% efficiency/ no loss of signal

(c) 1 In glass, there is no regular arrangement of particles.

1 In diamond, the atoms are arranged in an orderly/ giant tetrahedral and closely-packed structure.

SH

H

H

S

H

sp3hybrid orbital of S atom [1]

1sorbital of H atom [1]



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CONFIDENTIAL*/SULIT* 3

1 Trigonal bipyramidal

(iv) 1 5 big iodine atoms cause steric hindrance

6 (a) (i) Zn(s) + Cu2+

(aq) Cu(s)+ Zn2+

(aq)From data booklet:

1 Zn2+

+ 2e- Zn - 0.76 V

Cu2+

+ 2e- Cu + 0.34 V

1 E.m.f . cell , E

cell

= + 0.34(- 0.76) = + 1.10 V

1 At equilibrium, Ecell = 0 V

Overall electrochemical equation is a follows.

Zn(s) + Cu2+

(aq) Zn2+

(aq) + Cu(s) E

cell= +1.10 V

1 0 = 1.10][

][log

2

059.02

2

Cu

Zn

1 K = 1.94 x 1037

(ii) Using ba

dc

cellcellBA

DC

nEE

][][

][][log

059.0

4.0

8.0log

2

059.010.11

cellE

09.11 cell

E V

(b) 1 2H+(aq) + SO3

2-(aq) H2O (l) + SO2(g) H

H2(g) + S(s) + 3/2O2 2H+(aq) + SO3

2-(aq) (i) - 623

S(s) + O2(g) SO2(g) (ii) -296

H2(g) + O2(g) H2O (l) (iii) -286

1 (iii) + (ii)(i) //

{[H2(g) + O2(g)+ [S(s) + O2(g)][H2(g) + S(s) + 3/2O2]}

{[H2O (l)] + [SO2(g)][2H+(aq) + SO3

2-(aq)]}

0 {[H2O (l)] + [SO2(g)][2H+(aq) + SO3

2-(aq)]}

1 H = (-286) + (-296)(-623) = + 41 kJ

(c) 1 A buffer solution is capable of maintaining the pH of its solution when a

small amount of acid or alkali is added to it.

1 H2CO3 H++ HCO3

-

1 NaHCO3 Na++ HCO3

-

1 When a small amount of acid is added, the hydrogen ion reacts with the HCO3-

ion //H

++ HCO3

- H2CO3

1 When a small amount of alkali is added, the hydroxide ion reacts with the

acid H2CO3 // OH-+ H2CO3H2O + HCO3

-

7 (a) 1 MCO3(s) MO(s) + CO2(g)* (*Physical state is optional)1 Thermal stability of carbonate increases as descending Group 2

1 Charge density of cation, M2+

decreases as descending Group 2 //Ionic charge of cation remains as 2+ and the cationic size increases as descending Group 2

1 The carbonate anion, CO32-

has relatively large electron cloud

1 Polarising power of cation, M2+

over the electron cloud of CO32-

ion gradually weaker //Electron cloud of carbonate anion is less polarised as descending Group



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(b) (i) 1 Electrolysis of molten bauxite with graphite anode and cathode

1 Cryolite (or) Na3AlF6; at about 950oC to 1000

oC

1 Cathode: Al3+

is reduced to Al

Al3+

+ 3e Al

1 Anode: O2

is oxidised to O2

2O2

O2+ 4e

(ii) 1 Light weight and strong //resistance to corrosion

(c) 1 Colourless gas is carbon dioxide.

1 Aluminium ion has high charge density.

1 The aluminium sulphate aqueous solution contains Al(H2O)63+

hydrated ions //

Al3+

(aq) + 6H2O(l) [Al(H2O)6]3+

(aq)

1 Al(H2O)63+

ion hydrolyses to produce H+/ H3O

+ // the salt solution is acidic //

Al(H2O)6]3+

(aq) + H2O(l) [Al(H2O)5 (OH)]2+

(aq) + H3O+(aq)

1 2Al(H2O)63+

(aq) + 3CO32

(aq) 2Al(OH)3(H2O)3(s) + 3H2O (l) + 3CO2(g)

8 (a) 1 The high temperature in the car engines N2to combine with O2to form NO(g).

1 N2(g) + O2(g) 2NO(g)

1 2NO + 2CO N2+ 2CO2// 2NO N2+ O2

(b) 1 HCl is thermally more stable than HI

1 Purple colour = I2(g)1 2HI H2 + I2

(c) (i) Co : N : Cl : H

19.5852.23 :

0.1400.28 :

5.3553.42 :

0.1

95.5

0.40 : 2.0 : 1.20 : 6.0

1 1 : 5 : 3 : 15

1 Empirical formula of Q = CoCl3(NH3)5

1 (CoCl3(NH3)5)n = 250 ; n =1

1 Q = [CoCl(NH3)5]2+

. 2Cl

(ii) 1 Co3+

= [Ar] 3d6, 3dorbitals are partially filled.

1 Under the influence of ligands, the 3dorbitals are split into 2 groups1 dd transition happens

1 Energy difference falls in the visible region

9 (a) 1 CH3COOH, HCOOH, ClCH2COOH

1 RCOOH(aq) + H2O(l) RCOO(aq) + H3O

+(aq)

Acid Conjugate base

1 CH3is electron releasing group and Cl is electron withdrawing group

1 CH3of ethanoic acid causes OH bond of theCOOH group to be less

polarised, thus, less able to ionise. //

CH3of ethanoic acid destabilises the CH3COOconjugate base and

shifting the equilibrium position to the left.

1 Cl of chloroethanoic acid causes OH bond of theCOOH group to be

more polarised, thus more able to ionise. //

Cl of the chloroethanoic acid stabilises the CH3COO conjugate base, thus, shifting the

equilibrium position to the right.



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(b) (i) 1 Reagent and condition: Acidified KMnO4solution; room temperature.

1 Cyclohexene decolourises the purple colour of acidified KMnO4solution while no obvious

observation for cyclohexane.

1 OH

+ (O) + H2O

OH

(ii) 1 Reagent and condition: Acidified KMnO4solution; Heat

1 Toluene decolourises the purple colour of acidified KMnO4solution while

no obvious observation for benzene.

1

(c) 1 Free radical substitution

1 Cl2 2Cl

1 CH3CH2CH3+ Cl (CH3)2 CH + HCl

1 (CH3)2 CH + Cl2 (CH3)2 CHCl + Cl

10 (a) (i) 1 phenol1 amide

(ii) 1 Alkaline hydrolysis

1 NaO NH2

1 CH3COONa

(b)

NO2 NO2

50oC-60

oC

CH3[1] + [1] [1] [1]

(c) H2N-*CH-COOH H2N*CHCOOH

CH2 CH2

OH COOH

[1] [1]

1 Has a carbon chiral

1 shown as * in the structure

1 Mirror images are non-superimposable1 rotates plane-polarised light

COOH + H2O

CH3Cl / FeCl3Conc H2SO4 /

Conc HNO3

CH3 + 3(O)

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