Stpm Trial 2012 Chemistry Qa Kelantan

JABATAN PELAJARAN KELANTAN

TRIAL EXAMINATION

2012

CHEMISTRY (KIMIA)

SIJIL TINGGI PERSEKOLAHAN MALAYSIA (MALAYSIA HIGHER SCHOOL EDUCATION)

PAPER 1 (KERTAS 1) MULTIPLE-CHOICE (ANEKA PILIHAN)

One hour and forty-five minutes (Satu jam empat puluh lima minit)

Instructions to candidates :

DO NOT OPEN THIS BOOKLET UNTIL YOU TOLD TO DO SO

There are fifty questions in this paper. For each question, four suggested answers are

given. Choose one correct answer and indicate it on the multiple-choice answer sheet

provided.

Read the instructions on the multiple-choice answer sheet very carefully.

Answer all questions. Marks will not be deducted for wrong answers.

Arahan kepada calon :

JANGAN BUKA BUKU SOALAN INI SEHINGGA ANDA DIBENARKAN

BERBUAT DEMIKIAN

Ada lima puluh soalan dalam kertas ini. Bagi setiap soalan, empat cadangan

jawapan diberikan. Pilih satu jawapan yang betul dan tandakan jawapan itu pada

helaian jawapan aneka pilihan yang dibekalkan.

Baca arahan pada helaian jawapan aneka pilihan itu dengan teliti.

Jawab semua soalan. Markah tidak akan ditolak bagi jawapan yang salah.

This question paper consists of 18 printed pages

(Kertas soalan ini terdiri daripada 18 halaman bercetak)

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* This question paper is CONFIDENTIAL until the examination is over. CONFIDENTIAL*

2

Section A

Four suggested answers labeled A, B, C, and D are given for each question. Choose

one correct answer.

1 The unit cell of an element M is shown below:

Given the volume of the unit cell is α cm³ and the molar volume of M atoms is b

cm³, what the value for the Avogadro constant?

A

B

×14

C

×12

D

× 4

2 Copper is usually obtained as a mixture of 69.09% 63

Cu isotope and 30.91% 65

Cu

isotope. If the masses of 63

Cu and 65

Cu isotopes are 62.93 amu and 64.93 amu

respectively, what is the relative atomic mass of copper?

A 63.62

B 63.55

C 63.93

D 64.31


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3 What is the maximum number of electrons in third shell of an atom?

A 2

B 8

C 18

D 32

5 Which of the following properties show a gradual increasing trend with

increasing proton number for the elements Sc and Cu?

A Density

B Boiling point

C Melting point

D First ionisation energy

6 Ar, K+, and Ca

2+ are isoelectronic. The order of increasing radii is

A Ca2+

< K+ < Ar

B Ca2+

< Ar < K+

C Ar < Ca2+

< K

+

D K+ < Ar < Ca

2+

4 An element M has the following electron configuration.

What is M?

[Proton numbers: Ti = 22; V = 23; Mn = 25; Fe = 26; and Ni = 28]

A Nickel in [Ni(NH3)6]2+

B Iron in Fe2(SO4)3

C Titanium in TiO2

D Manganese in MnO42−

3d

(Ar)

3s


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7 Which element possesses the strongest metallic bond?

A Magnesium

B Calcium

C Sodium

D Lithium

8 XH3 is a gaseous hydride of an element in Group 15 of Periodic Table. Which of

the following shapes is most appropriate for the hydride molecule?

A V-shaped

B Trigonal pyramid

C Plane trigonal

D Tetrahedral

9 Which of the following molecules is polar?

A SF6

B BCl3

C SnCl4

D CH3Cl

10 Magnesium metal is a good conductor of electricity. Which of the following

statements is true of the metal?

A The 3s orbital forms the valence and conduction band

B The electrons in 3s and 3p orbitals are delocalised

C The energy gap between the valence band and the conduction band is large

D Its conductivity is lower than silicon when the temperature increase


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11 The thermal decomposition of hydrogen iodide is a second order reaction.

Which of the following graphs is correct for this reaction?

A

B

C

D

2 HI(g) H2(g) + I2(g)

Time

[HI]

Time

Rat

e

[HI]2

lg [HI]

Time


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12

The equilibrium constant, Kc, for the reaction

is given by

A

C

B D

13 In the Contact process, sulphur dioxide is converted into sulphur trioxide

according to the following equation:

∆H is negative

Which of the following sets of conditions at equilibrium would give the highest

yield of sulphur trioxide?

Temperature Pressure Catalyst

A High High Present

B Low High None

C High Low None

D High High None

14 The solubility product of silver chloride is 1.0 × 10-10

mol2 dm

-6. What mass of

silver chloride will dissolve in 1 dm3 of a solution of sodium chloride with a

concentration of 0.10 mol dm-3

?

A 1.0 × 10-14

mol dm-3

B 1.0 × 10-10

mol dm-3

C 1.0 × 10-9

mol dm-3

D 1.0 × 10-5

mol dm-3

2NH3(g) + 3CuO(s) 3Cu(s) + N2(g) + 3H2O(g)

[Cu]3[N2][H2O]

3

[NH3]2[CuO]

3

[N2] [H2O]3

[NH3]2

[N2][H2O]

[NH3]

3[N2] [H2O]

2 [NH3]

2SO2(g) + O2(g) 2SO3(g);


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15 Which of the following species could behave as an acid and a base according to

Bronsted- Lowry theory?

A HCO3-

B CO32-

C OH-

D HCl

16 The partition coefficient of substance X between ether and water is 8.0 at room

temperature. An aqueous solution containing 5.0 g of X in 100cm3 of water is

extracted with 100cm3

of ether. What is the maximum mass of X that can be

extracted into the ether layer?

A 0.35 g

B 2.34 g

C 4.44 g

D 3.98 g

17 The chromatogram below is obtained from thin layer chromatography of a sample

of amino acid P, Q, R and S.

Base on the Rf value in the table below, deduce the amino acids present in the

sample. Amino acid Rf value

P 0.16

Q 0.32

R 0.68

S 0.84

A P and S

B Q and R

C P and Q

D P and R

8.4 cm

6.8 cm

Solvent front

Base line

10 cm


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18 Consider the half-cells below:

Cu+ + e

- Cu E

ø = +0.52 V

Cu2+

+ e- Cu

+ E

ø = +0.52 V

What is the Eø for the reaction :

2Cu+ Cu

2+ + Cu

A

-0.68V

C +0.36V

B

-0.36V

D

0.00V

19 Which of the following is not true for the Daniel cell?

A The e.m.f is 1.10V

B Its anode has a negative charge.

C It function as an electrolysis cell

D Electrons flow from the zinc electrode to the copper electrode

20 Which of the following compounds is expected to have the most negative lattice

energy?

A LiF

B LiBr

C NaCl

D NaF

21 Which of the following processes involves the enthalpy of formation?

A H2(g) + O(g) H2O(l)

B 2CO(g) + O2(g) 2CO2(g)

C Na+(g) + Cl

- (g) NaCl(s)

D 2C(s) + 3H2(g) + ½ O2(g) C2H5OH(l)


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23 Which of the following elements in the same period of the Periodic Table has the

highest boiling point?

A Sodium

B Sulphur

C Aluminium

D Magnesium

24 Which of the following shows the changes in properties of oxides of Group 14

elements (carbon to lead) in the Periodic Table?

A Acidic → basic → neutral

B Acidic → neutral → basic

C Acidic → amphoteric → basic

D Basic → amphoteric →acidic

25 Which of the following statements about Group 14 elements (carbon to lead) of

the Periodic Table is true?

A Only CCl4 is hydrolysed by water.

B Only oxides of tin and lead are amphoteric.

C All oxide of elements give oxygen gas when heated strongly.

D +2 oxidation state of elements becomes more stable when moving down the

group.

22 Which of the following is the correct physical property of elements across the

Third Period from sodium to chlorine in the Periodic Table?

A Size of atoms increases.

B Melting point decreases.

C Electronegativity decreases.

D First ionization energy increases.


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26 Which statement about the properties of the tetrachlorides of Group 14, CCl4 to

SnCl4, is correct?

A They are all polar molecules.

B Their melting points increase down the group.

C Their boiling points decrease down the group.

D Tin (IV) chloride is the only ionic tetrachloride.

27 Nitrogen is very non-reactive at low temperatures because the gas

A has half-filled p orbitals.

B has high atomisation energy.

C exists as diatomic molecules.

D has a stable electron configuration.

28 Which of the following statements is not true about halogens?

A Solubility in water decreases.

B They exist as diatomic molecules.

C Reactivity with hydrogen increases down the group.

D They become darker in colour moving down the group.

29 Which of the following elements in the first series of transition elements does not

show general characteristics of a transition element?

A Copper

B Nickel

C Scandium

D Vanadium


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30 An organic compound has the structure

Which of the following is not true regarding the compound?

A It exihibits geometrical isomerism

B It exihibits optical isomerism

C It decolorises acidified potassium manganate (VII)

D It is insoluble in water

31 Benzene reacts with a mixture of concentrated nitric acid and concentrated sulphuric

acid to produce nitrobenzene according to the equation:

C6H6 + HNO3 C6H5NO2 + H2O

What is the function of sulphuric acid in the above reaction?

A To protonate the nitric acid

B To eliminate the water produced

C To prevent di-substitution from occurring

D To prevent oxidation of benzene by nitric acid

32

The reaction mechanism between chlorine and methane is shown below:

Cl2 2Cl· (i)

CH4 + Cl· CH3· +HCl (ii)

CH3· + Cl2 CH3Cl + Cl· (iii)

Which of the following is not true regarding the reaction?

A Reaction (i) requires ultra-violet light

B

The reaction can occur in the dark if the mixture is heated with benzoyl

peroxide

C CH3Cl is the only product formed

D A little C2H6 is also formed in the reaction

H2SO4

CH3

C

CH3 CH2


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33 The scheme below shows the production of compound Z from 2-propanol.

Which of the following are X, Y and Z?

X Y Z

A Br2

B Br2

C PBr3

D PBr3

CH3CHOH

CH3

CH3CHBr

CH3

CH3

CH3CHMgBr

X

Y Z H2O/H

+

CrO3 Mg

CH3C=O

CH3

CH3

CH3CH C

CH3

CH3

OH

CH3C=O

CH3 CH3

CH3CHCH2CH2CH2OH

CH3C=O

CH3

CH3C=O

CH3

CH3

CH3CH C

CH3

CH3

OH

CH3

CH3CH C

CH3

CH3

OH


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35 When a compound P which does not react with acidified solution of potassium

dichromate (VI), is heated with aluminium oxide, compound Q is produced. The

compound Q can decolourise bromine water. If Q is treated with hydrogen bromide,

2-bromo-2-methylpropane is produced.

Compound P could be

A butan-2-one

B propan-2-ol

C butan-2-ol

D 2-methylpropan-2-ol

36 Which of the following compounds could be the main product when ethanoic acid is

treated with lithium tetrahydridoaluminate (III) ?

A CH3CH3

B CH2=CH2

C CH3CHO

D CH3CH2OH

34 A compound Z shows the following properties:

(i) Reacts with sodium to give a combustible gas

(ii) Reacts with benzoyl chloride to give a precipitate

(iii) Reacts with aqueous solution of sodium hydroxide to give a salt

Compound Z could be

A

B

C

D

OH

OH

CH2OH

CHO


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37 Acarol is sold as insecticides for fruits and vegetables.

Acarol

The last step in its manufacture is esterification. Which alcohol is used to make the

above ester?

A Di(4-bromophenyl)methanol

B Methanol

C Propan-1-ol

D Propan-2-ol

38 The correct order of increasing basicity of ammonia, ethylamine and phenylamine is

A ammonia < ethylamine < phenylamine

B phenylamine < ammonia < ethylamine

C ethylamine < phenylamine < ammonia

D phenylamine < ethylamine < ammonia

39 Which of the following statements about 2-aminopropanoic acid and aminoethanoic

acid is not true?

A both are optically active

B Both form a salt with mineral acid

C Both react with nitric (III) acid

D Both form zwitterions in aqueous solutions

C

│

│

Br │

│

C O CH

Br

OH CH3

CH3

│

=

O


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Section B

For each of the questions in this section one or more of the three numbered

statements 1 to 3 may be correct. Decide whether each of the statements is or is not

correct. The responses A to D should be selected on the basis of the following.

40 Which of the following pairs are monomers of a condensation polymer?

A CH3O2CCCH2CH2COOCH3 and CH2=CHCH=CH2

B

and H2N(CH2)NH2

C

O=CHCH2CH2CH=O and

D

and H2NCH2CH2NH2

41 Which of the following statements are correct for the elements in the Periodic

Table?

1 The elements are arranged in the order of increasing proton number.

2 The atomic radii increases down a group.

3 Electronegativity increase across a period.

42 Which of the following are true of a first order reaction?

1 The rate constant is dependent on the temperature.

2 The half-life is independent of the initial reactant concentration

3 The units of the rate constant is time-1.

A B C D

1 only

is correct

1 and 2

are correct

2 and 3 only

are correct.

1 , 2, and 3

are correct.

OH HO

CH3 CH3

COOH HOOC


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43 In the Nernst equation,

Ecell = Eocell +

ln

Which of the following quantities can have both positive and negative values?

1 [Oxidation form]

[reduced form]

2 Eø

3 T

44 Which of the following properties of ammonia can be explained in terms of

hydrogen bonding?

1 It is very soluble in water.

2 It is a base.

3 The liquid form contains the ions NH4+ and NH2

-

45 Why are most catalysts transition elements or their compounds?

1 They have a high charge density.

2 They show variable oxidation states.

3 They have available d orbitals for bonding.

46 Ethene and ethane can be differentiated by using

1 acidified KMnO4

2 bromine in the absence of light

3 concentrated sulphuric (VI) acid

A B C D

1 only

is correct

1 and 2

are correct

2 and 3 only

are correct.

1 , 2, and 3

are correct.

ln


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48 Oxidation of pentane-2-ol produces compound X. X is expected to

1 give an orange precipitate with 2,4-dinitrophenylhydrazine

2 give a negative reaction with Tollen’s reagent

3 give a yellow precipitate with alkaline iodine

A B C D

1 only

is correct

1 and 2

are correct

2 and 3 only

are correct.

1 , 2, and 3

are correct.

47 One mole of organic compound, X, reacts with two moles of sodium hydroxide

on heating. X could be,

1

2

3

CHCl2

Cl

Cl

CH2Cl Cl


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49 Z, C2H5NO2, reacts with nitrous acid to release nitrogen gas. 10cm3 of a solution

containing 0.75g dm-3

of Z requires 10cm3 of 0.01 mol dm

-3 sodium hydroxide

for complete reaction. Which of the following is/ are true regarding Z?

1 It is an amino acid

2 It contains one –COOH group in its molecule

3 It is an amide

50 ‘Clearfilm’ is manufactured from a polymer made by copolymerizing

1

2

3

END OF QUESTION PAPER

CH2=CHCl and CH2=CCl2

--CHCl—CH2—CCl2--

--CH2—CHCl—CCl2--

--CCl2—CCl2—CH2—CHCl--


CONFIDENTIAL* 962/2

This question paper is CONFIDENTIAL until the examination is over. CONFIDENTIAL*

2

SECTION A

Answer all the questions in this section.

1(a) Nitrogen is used in the packing of junk food to keep the food fresher for a longer

period.

(i) Write the electronic configuration of the nitrogen atoms. [1 mark]

………………………………………………………………………………………………….

(ii) Nitrogen can form the NCl3 molecule only, but phosphorous can form both the PCl3

as well as PCl5 molecule. Draw the Lewis diagram for NCl3 and PCl5 and Predict the polarity

NCl3 and PCl5. [4 marks]

(iii) Show and label the overlapping orbital of N2H4. [3 marks]


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(b) The diagram below shows the four electron transitions in the hydrogen atom.

(i) Base on the energy level diagram, sketch the line spectrum formed

from these transition. [2 marks]

2 Some standard electrode potentials are shown below.

Half Reaction Eo/V

Ag+ + ē Ag

+ 0.80

½ Cl2 + ē Cl-

+ 1.36

Cu2+

+ 2ē Cu

+ 0.34

Fe3+

+ ē Fe2+

+ 0.77

½ I2 + ē I-

+ 0.54

(a) The diagram below shows an incomplete cell consisting of Cu/Cu2+

and Ag/Ag+

half-cells under standard conditions.

Energy

n=5

n=4

n=3

n=2

n=1


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4

(i) Complete and label the diagram to show how the cell potential of this cell

could be measured. [2 marks]

(ii) On the diagram, show the direction of electron flow in the circuit. [1 mark]

(iii) Write the cell diagram for the above set-up. [1 mark]

………………...............................................................................................................

(iv) Write the overall cell reaction. [1 mark]

……………….................................................................................................................

(v) Calculate the standard cell potential. [1 mark]

(vi) Calculate the cell potential if the solution in the right beaker is replaced with

0.10 mol dm-3

aqueous silver nitrate, other factors remaining unchanged. [ 2 marks]

(b) Chlorine will oxidise Fe2+

to Fe3+

but iodine will not. Explain why using the electrode

potential data. [2 marks]

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................


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3(a) (i) What do you understand by the term “complex ion”? [2 marks]

……………………………………………………………………………………………

……………………………………………………………………………………………

(ii) 1,2-ethenediamine is a chelating ligand. Explain the term ‘chelating ligand”.

[1 mark]

………………………………………………………………………………………………….

(b) A series of experiments were carried out on an aqueous solution of copper(II) sulphate.

Experiment Observation

Aqueous sodium hydroxide is added to

copper(II) sulphate solution

A blue precipitate is formed

Aqueous ammonia is added to

copper(II) sulphate solution until in

excess

The blue precipitate dissolves and a dark

blue solution is obtained

(i) Write the formula of all the complex ions in the experiments [2 marks]

……………………………………………………………………………………………………………

(ii) Arrange the ligands in order of increasing strength with respect to copper(II). Explain

your answer. [2 marks]

…………………………………………………………………………………………………………..

(iii) Explain why transition element complex are often coloured , whereas

compounds of other metals are usually white. [3 marks]

……………………………………………………………………………………………………………

…………………………………………………………………………………………………………….

…………………………………………………………………………………………………………….

……………………………………………………………………………………………………………


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4(a) “Aspartame” is an artificial sweetener which is 180 times sweeter than sugar.

The structural formula of “aspartame” is

H2N – CH - CO – NH – CH –COO – CH3

| |

CH2 CH2

| |

COOH

(i) Name four different functional groups in the molecule of “aspartame”.

[4 marks]

……………………………………………………………………………………………

(ii) Identify two of the functional groups which contribute to its solubility in

water. Give reasons for your answer. [2 marks]

……………………………………………………………………………………………

……………………………………………………………………………………………

(b) “Aspartame” can be hydrolyses into its constituent parts under certain conditions.

(i) Suggest the reagent and condition for hydrolysis. [1 mark]

………..………………………………………………………………………………………..

(ii) Draw the structural formulae of all organic molecules obtained by hydrolysis

‘aspartame”. [3 marks]


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SECTION B

Answer any four questions in this section.

5(a) Krypton is used to fill fluorescent lights and photo graphic flash lamps.

(i) Use the following data to sketch a phase diagram for krypton [4 marks]

(ii) What is meant by the term triple point ? [1 mark]

(iii) What are the physical states of krypton under P = 5.3 atm , T = -153°C and

P= 65 atm , T = 250°C [2 marks]

(iv) Can a sample of gaseous krypton at room temperature be liquefied by raising

its pressure? Explain why? [2 marks]

(b) At 101 kPa, the boiling points of pure ethanol and water are 78.5°C and 100.0°C

respectively. A solution of ethanol and water forms an azeotropic mixture with a boiling

point of 78.2°C. The percentage by mass of ethanol in the mixture is 96.0% ethanol.The

boiling point-composition curve for the ethanol-water mixture is shown below.

(i) This mixture does not obey Raoult’ law. State the type of deviation and

explain. [3 marks]

(ii) Briefly explain how pure ethanol can be obtained from a 70% ethanol mixture.

[3 marks]

Pressure/atm Temperature/°C

Triple point 0.175 -169

Critical point 54 -63

Melting point 1 -156.6

Boiling point 1 -152.3

Temperature/oC

(°C)

0% 100%

78.5

100

96%

78.2

composition


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6(a) 1.00 g of solid potassium hydroxide was dropped into 50.0 cm3 (50.0 g) of aqueous

hydrogen chloride (slightly in excess) contained in a polystyrene cup. A temperature change

from 30.0oC to 40.0

oC was recorded with a thermometer in the solution.

(The specific heat capacity of the solution is 4.0 J K-1

g-1

).

(i) Define the heat of neutralization. [2 mark]

(ii) Write a balance equation for the above equation. [1 mark]

(iii) From the experimental data provided, calculate ΔH for the reaction.

[3 marks]

(iv) Give one important reason why it is preferable to use a polystyrene cup

instead of a glass beaker. [1 mark]

(v) Why should the solution stirred during the reaction. [1 mark]

(b) Octane, C8H18 is used as fuel.

(i) Define the heat of combustion with related to octane . [1 mark]

(ii) Write a balance equation for the combustion of octane in excess oxygen.

[1 mark]

(iii) Calculate the standard enthalpy of combustion of octane by using the

following information.

ΔHf of CO2 -394 kJ mol-1

ΔHf of H20 -286 kJ mol-1

ΔHf of C8H18 -250 kJ mol-1

[3 marks]

(iv) How is the knowledge of standard enthalpy of combustion useful to a chemist

other than that of as fuel? [2 marks]


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7(a) The table below gives the melting point for each of the Period 3 elements Na to Ar.

(i) Describe and explain the difference between the electrical conductivities of the

elements aluminium, silicon and phosphorus. [4 marks]

(ii) When aluminium combines with chlorine, it results in the formation of

aluminium chloride. Aluminium chloride can further react with chloride ions as

shown by the equation below.

AlCl3 + Cl– → AlCl4

–

Explain how the bond between aluminium chloride and the chloride ion is

formed. [3 marks]

(b) The table below shows the elements in group II of the periodic table.

Element

Beryllium

Magnesium

Calcium

Strontium

Barium

(i) State and explain the differences in bonding between beryllium chloride and

magnesium chloride. [3 marks]

(ii) Sulphates of the Group II elements have different solubilities. State and

explain the trend in solubilities. [2 marks ]

(iii) A student on a field trip investigates some disused mining pools which have

been flooded for some time. The presence of barium ions in the water is to be

demonstrated by precipitating barium(II) sulphate. The solubility of barium(II)

sulphate in water at 25oC is 1.05 x 10

-5 mol dm

-3. Calculate its solubility product

and state one use that depends upon this insolubility. [3 marks]


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8 Ammonia is one of the best-known compounds. It is prepared industrially from

nitrogen and hydrogen by the Haber process. The equation for the main reaction in the Haber

process is

N2(g) + 3H2(g) 2NH3(g) ΔH = negative

The table below gives information about the percentage yields of ammonia obtained in the

Haber process under different conditions.

Pressure/atm Temperature/°C

200 300 400 500

10

100

200

300

400

600

50.7

81.7

89.1

89.9

94.6

95.4

14.7

52.5

66.7

71.1

79.7

84.2

3.9

25.2

38.8

47.1

55.4

65.2

1.2

10.6

18.3

24.4

31.9

42.3

(a) (i) From the table, state the conditions that gives the higher yield of ammonia.

[2 marks]

(ii) State a suitable catalyst .

[1 mark]

(b) Ammonia can be oxidised by air to form nitrogen oxide.

4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) ΔH= -909kJmol-1

This reaction forms the first stage in the manufacture of nitric acid from ammonia.

Using Le Chatelier’ s principle state and explain the change in equilibrium yield

of nitrogen oxide caused by:

(i) Increasing the pressure at constant temperature [3 marks]

(ii) Increasing the temperature at constant pressure [3 marks]

(iii)The industrial process is operated at a temperature of about 900°C. Suggest a

reason for this temperature. [2 marks]

(c) An aqueous solution of nickel(II) chloride reacts with aqueous ammonia to form a

precipitate X. The precipitate X dissolves in excess aqueous ammonia to give a

solution Y. State the colours of X and Y and also write the chemical formula of each.

[4 marks]


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9(a) An amount of 0.01 mole of a hydrocarbon is burnt in excess oxygen. The products of

the combustion are passed through anhydrous calcium chloride and then through potassium

hydroxide solution. The masses of anhydrous calcium chloride and potassium hydroxide

solution increase by 0.72 g and 1.76 g respectively.

(i) Determine the empirical formula of the hydrocarbon. [4 marks]

(ii) Determine the relative molecular mass of the hydrocarbon and hence its

molecular formula. [4 marks]

(b) Draw the structure of the major product of each of the following reactions.

(i) + NH3 ethanol

Δ [1 marks]

(ii) (CH3)2CBr2 + NaOH [1 marks]

(iii) [1 marks]

(c) The molecular structure of compounds T is given below.

What are the organic products expected when T is reacted with each of the following

reagents ?

(i) H2 / Pt [1 marks]

(ii) LiAlH4 , followed by H3O+ [1 marks]

(iii) I2 / NaOH [2 marks]

Br

CHO

(i) CH3CH2MgBr

(ii) H3O+

Δ

O

║

CH3C CH2 =O


CONFIDENTIAL* 962/2


12

10(a) Natural rubber is cis-poly(2-methyl-1,3-butadiene). Physical properties are altered

after vulcanisation process.

(i) Draw a repeating unit for the above polymer. [1 mark]

(ii) What characteristic must be present in the molecule of the polymer so that the

vulcanisation process can be carried out? [1 mark]

(iii) State two changes in the physical properties of natural rubber after the

vulcanisation. [2 marks]

(iv) If an excess of the vulcanising agent is added during the vulcanisation process,

what would be the change in the physical properties of the natural rubber ? [1 mark]

(v) State the vulcanising agent and draw the structure of vulcanised rubber.

[2 marks]

(vi) Natural rubber is a type of elastomer. What would you understand by the term

elastomer?

[1 mark]

(b) The possible mechanism for hydrolysis of 3-bromo-3-methylhexane by hydroxide ion,

OH- is as follows:

slow

C3H7- C(OH)(CH3)-C2H5

(i) Write the rate equation for the above mechanism. [1 mark]

(ii) What will happen to the rate of reaction if OH- is replaced by CN

- ?

Explain your answer. [2 marks]

(iii) Name the above mechanism. [1 mark]

(iv) 3-bromo-3-methylhexane shows stereoisomerism. Name the type of isomerism

and draw all the structural formulae of this isomers. [3 marks]

C3H7- C(Br)(CH3)-C2H5

C3H7- C(CH3)-C2H5 + OH-

+

C3H7- C(CH3)-C2H5 +

fast


STPM TRIAL 2012

Suggested Answer

Chemistry 962/1

1 D 11 C 21 D 31 A 41 D

2 B 12 B 22 D 32 C 42 D

3 C 13 B 23 C 33 D 43 B

4 B 14 C 24 C 34 B 44 A

5 A 15 A 25 D 35 D 45 C

6 A 16 C 26 B 36 D 46 B

7 B 17 A 27 B 37 D 47 A

8 B 18 C 28 C 38 B 48 D

9 D 19 C 29 C 39 A 49 B

10 A 20 A 30 A 40 D 50 A


CONFIDENTIAL* 962/2 1

CHEMISTRY MARKING SCHEME

STPM TRIAL 2012

1 (a) (i) N : 1s2 2s

2 2p

3 [1]

(ii)

NCl3 PCl5

NCl3 : Polar molecule PCl5: non-polar molecule

[1]+[1]

[1]+[1]

(iii) Overlapping orbital of N2H4

Label the hybrid orbital

Show overlapping

Label sigma(σ) bond

[1]

[1]

[1]

(b) (i)

[1]+[1]

TOTAL MARKS

10

Increasing frequency

N N

H

H

H

H

σ

σ

σ

σ

P

• x

• x

• x

• x

• x

Cl

Cl

Cl

Cl

Cl

• •

• • • •

• •

• •

• •

• • •

•

• •

• •

• •

• •

• •

• •

• •

P

• x

•x

• x

x x

• •

•• ••

••

••

••

• •

• •

• •

N Cl

Cl

Cl



2 (a) (i)

[1]

[1]

(ii) Direction of electron flow from Cu(s) to Ag(s) (must be in/close to wire)

[1]

(iii) Cu(s)Cu2+

(aq)// Ag+(aq)Ag(s)

[1]

(iv) Cu(s) + 2Ag+(aq) Cu

2+(aq) + 2Ag(s)

[1]

(v) Eocell = (– 0.34) + ( +0.80) or

= + 0.46 V

[1]

(vi) Nernst Equation

2

2

][

][log

2

059.0

Ag

CuEE o

cellcell

or

V40.0

10.0

00.1log

2

059.0)46.0(

2

[1]

[1]

(c) Standard electrode potential for chlorine is more positive than Fe3+

therefore it is a better oxidising agent than Fe3+

(do not accept Eo is

larger or smaller)

Standard electrode potential for iodine is less positive than Fe3+

therefore it is a poorer oxidising agent than Fe3+

.

(Accept release of electrons/equilibrium arguments)

Or calculation

[1]

[1]

TOTAL MARKS 10



3 (a) (i) An ion which formed when a metallic ion is bonded to a group of ligand

by dative bonds

[1]

[1]

(ii) Ligand that can donate more than one lone pair electrons

[1]

(b) (i)

[Cu(H2O)6]2+

; [Cu(H2O)4(OH)2] ; [Cu(NH3)4]2+

3 corrects

2 corrects

[2]

[1]

(ii) H2O < OH- < NH3

A stronger ligand is able to displace a weaker ligand from the complex

ion

[1]

[1]

(iii) Transition metal ions have incomplete 3d-subshell / d1 to d

9

d-d electronic transition is possible

non transition metal / other metal have either completely filled 3d orbitals or

no 3d electron or no d-d electronic transition

[1]

[1]

[1]

TOTAL MARKS 10



4 (a) (i) Carboxyl, amino, ester and amide [4]

(ii) Amine and carboxylic acid.

This amino acid can exist as zwitterions

Attraction between this ion with polar water molecules is responsible for

it solubility

[1]

[1]

(b) (i) Heat with dilute sulphuric acid / H2SO4 / H+ [1]

(ii)

[1]

+ _

H3N – CH –COO

|

CH2

|

[1]

[1]

TOTAL MARKS 10

OH

|

H - C - H

|

H

+ _

H3N – CH – COO | CH2 | COOH



P/atm

T/°C

Liquid

54 Critical point

0.175 Triple point

-169 -63

5 (a) (i)

Correct x-axis , y-axis and label Correct curve All point label All phases label

[1]

[1]

[1]

[1]

(ii) Conditions of temperature and pressure under which a substance can exist in the solid, liquid and gas in equilibrium

[1]

(iii) Liquid

Gas

[1]

[1]

(iii) Cannot Because room temperature is above critical temperature

[1]

[1]

(b) (i) Positive deviation

Because hydrogen bonds /attractive forces between ethanol and water

molecules are weaker than those between the pure molecules

Hence the ethanol and water molecules easily escape from this mixture.

or

total vapour pressure is higher than predicted

[1]

[1]

[1]

(ii) Fractional distillation.

Distillate is an azeotropic mixture / 96% ethanol.

Pure ethanol can be obtained by adding anhydrous calcium oxide to

remove water.(any other drying agent)

[1]

[1]

[1]

15

Solid

Gas



6 (a) (i) The standard enthalpy of neutralization, ΔHneut is the enthalpy

change when one mole of hydrogen ions, H+(aq), reacts with one

mole of hydroxide ions, OH-(aq),

to form one mole of water under standard condition.

[1]

[1]

(ii) KOH(aq) + HCl(aq) KCl(s) + H2O(l) [1]

(iii) Molar mass of KOH = 39.1 + 16.0 + 1.0 = 56.1

Amount of KOH used =

= 0.0179 mol

Or = 1.79 x 10-2

mol

Heat evolved = mcѲ

Or = 50.0 x 4.0 x (40.0 -30.0)

= 2000 J or

= 2.00 kJ

ΔH = -

Or = -112 kJ mol-1

[1]

[1]

[1]

(iv) Polystyrene cup is a good heat insulator and has a low heat capacity.

[1]

(v) Stirring speeds up dissolving and so minimize heat loss during the

dissolving process by reducing the duration of the experiment.

Or

It also provides even distribution of temperature.

[1]

(b) (i) The standard enthalpy of combustion is the heat released when one

mole of octane is completely burned in excess oxygen under

standard condition.

[1]

(ii) 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O [1]

(iii) 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O

ΔHf : 2(-250) 0 16(-394) 18(-286)

or ΔH = [18ΔHf(H2O) + 16ΔHf(CO2)] – [2ΔHf(C8H18) +

25ΔHf(O2)]

= [18(-286) + 16(-394)] – [2(-250) + 25(0)]

= -10952 kJ mol-1

= -1.09 x 104 kJ mol

-1

[1]

[1]

[1]

(iv) When storing chemical substances with high enthalpy of combustion,

they must be protected from sunlight or sources of heat.

Or to present explosion

[1]

[1]

TOTAL MARKS 15



7

(a) (i) Aluminium is a good conductor.

Silicon and phosphorus are non-conductors.

Aluminium has metallic bond with delocalized electrons.

Silicon & phosphorus have localized electrons /do not have

delocalized electrons.

[1]

[1]

[1]

[1]

(ii) Dative bond

Electron pair/lone pair donated from Cl- to Al/AlCl3

Diagram

[1]

[1]

[1]

(b) (i) Beryllium chloride is covalent.

Magnesium chloride is ionic.

The beryllium atom is much smaller than the magnesium atom,

more difficult for it to transfer electrons to the chlorine atoms,

instead it shares the electrons

[1]

[1]

[1]

(ii) Solubility of the group 2 sulphates decreases down the group from

beryllium to barium.

Going down the group,

lattice enthalpy decreases slowly (since the sulphate ion is large )

but hydration enthalpy shows a larger decrease

hence the enthalpy of solution becomes more positive.

[1]

[1]

[1]

(iii) BaSO4(s) Ba2+

(aq) + SO42-

(aq) (1)

Each mole of barium sulphate dissolves to give 1 mole of barium

ions and 1 mole of sulphate ions in solution.

[Ba2+

] = 1.05 x 10-5

mol dm-3

[SO42-

] = 1.05 x 10-5

mol dm-3

Ksp = [Ba2+

][SO42-

]

[1]

[1]



= (1.05 x 10

-5)(1.05 x 10

-5) or

= 1.10 x 10-10

mol2 dm

-6

Use:

contrast medium used for X-ray imaging of the intestines/

gastrointestinal tract OR

white pigment for paints OR

component of oil well drilling fluid

[1]

[1]

TOTAL MARKS 15

8 (a) (i) High pressure or 600 atm

Low temperature or 200oC

[1]

[1]

(ii) Iron filling [1]

(b) (i) Yield or NO decrease

No of gas molecules increase (9 to 10)

The equilibrium shift to the left / backward

[1]

[1]

[1]

(ii) yield is reduced/ decrease

Forward reaction is exorthermic so

the equilibrium to the left

[1]

[1]

[1]

(iii) If temperature is reduced the yield is increased.

At lower temperature the rate of reaction will be very slow.

[1]

[1]

(c) X – Green, Ni(OH)2

Y – Blue, Ni(NH3)62+

[1+1]

[1+1]

TOTAL MARKS 15



9 (a) (i) CxHy + [ x + y/4]O2 → x CO2 + y/2 H2O

anhydrous CaCl2 absorbs water and KOH absorbs carbon dioxide-the

mass of water is 0.72 g and the mass of carbon dioxide is 1.76 g

Mass of C =

OR

= 0.48 g

The mass of C is 0.48 g.

Mass of H =

OR

= 0.08 g

The mass of H is 0.08 g.

Element C H

Mass 0.48 0.08

Number of moles

0.48

12.0

=0.04

0.08

1.0

=0.08

Mole ratio 1 2

Empirical formula is CH2

[1]

[1]

[1]

[1]

[1]

(ii)

The mass of hydrocarbon = mass of C + mass of H

= 0.48 + 0.08

= 0.56 g

Relative molecular mass = mass

mol

= 0.56 OR

0.01

= 56

(CH2)n = 56

or 14n = 56

or n = 4

Molecular formula is C4H8

[1]

[1]

[1]

[1]



(b)

(i)

(ii)

(iii)

(CH3)2C(OH)2 (CH3)2C=O

[1]

[1+1]

[1]

(c)

(i)

(ii)

(iii)

OH

|

CH3CCH2-

|

H

OH

|

CH3CCH2- --OH

|

H

O

║

+NaO

- CCH2- =O and CHI3

[1]

[1]

[1+1]

TOTAL MARKS

MAX

17

15

NH2

CH(OH)CH2CH3

OH



10 (a)

(i)

[1]

(ii)

(iii)

(iv)

(v)

(vi)

C= C or double bond

harder

more elastic

less sticky

[ any two ]

hard and brittle (both)

sulphur

Elastomer is polymer that stretches when pulled and return to their

length or shape when the force is released. /elastic

[1]

[1]+[1]

[1]

[1]

[1]

[1]

(b)

(i)

(ii)

(iii)

Rate = k [ C3H7-C(Br)(CH3)-C2H5 ]

constant or no change

because OH- ion does not involve in the rate of determining step

OR only reactant (3-bromo-3-methylhexane) affected by the rate of

hydrolysis

Nucleophilic subtituition

[1]

[1]

[1]

[1]

CH3 H

C = C

--- CH2 CH2----

CH CH2

S C = C CH3 H

CH CH2

C = C S CH3 H CH CH2

C = C CH3 H

CH2 CH

C = C CH3 H



(iv) Optical isomer

C3H7 C3H7

| |

C C

Br C2H5

CH3 C2H5 CH3 Br

[1]

[1]+[1]

TOTAL MARKS 15


Stpm Trial 2012 Chemistry Qa Kelantan

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