stpm trial 2009 che q&a (johor)

8/14/2019 STPM Trial 2009 Che Q&A (Johor)

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CONFIDENTIAL" 2

Section A

Four suggested answers labelled A, B, C and 0 are given for each question. Choose onecorrect answer. .

1. Which of the following sketches show part of the mass spectrum of the refrigerant,

CF 2CI2? [The isotopes are : 12C , 18F t Met 31CO

11 (, I

A c

mle J'IIlio

120 122 [24 120 122 124

B

'--'---'---'---. mle ratiomk: "no

120 122 124120 122 124

2. The unit cell of a metal M is shown below . Given the volume of the unit cell is V, cm 3 and

the volume of 1 mol of M atoms is V2 cm3• What is the value of the Avogadro constant?

g.(, ' f

-:i ./'

';5 j.....

e n' h..o t-,

. . /. .

A. V,/V,

c. 01,/ V,) x 7

•.

.

•

. . /

.....

/ '

c.

01,/V,)x4

01, /V,) x 14

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CONFIDENTIAL' 4

3. Antimony Sb, is in Group 15 of the Periodic Table. The ion below has a square-based

pyramidal shape.

1-1 ; HeF

l \ Be 60 Co N;o.Fl Ne ~ J ~ F F ~ ~ .-

Deduce the total number o f electrons around the antimony atom and the value of n?

)( n(n - t ) -\\ 0

Total number of elec;trons

10

10

12

12

value of "

1

2

1

2

\ /. (( I - I) ~ ' ) . (\-+ \ 4. Gaseous particle X has a proton number n and a charge of +1 . Gaseous particle Y has a

proton number of (0+1) and is isoelectronic with X. VVhich statement correctly describes X and

Y?

6.

0)B

c0

X has a larger radius than Y

X requires more energy than Y when the second electron is removed f

from each particle

X releases more energy than Y when an electron is added to each particle

X and Y belong to the same group in the Periodic Table

o H6,- 11 Y '" JH L C ~ L H

IH

VVhich of the following correctly describes the approximate values of the bond angles in

the molecule above?

6 y (J

A 90" 1800 90"

B 105' 160' 90"

.tZJ 120' 105' 109 '

0 120' 109' 109'

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CONFIDENTIAL' , 6

6. In which pair of m o ~ u t e s is the permanent dipole in molecule I greater than that in

molecule II?

B

C

D

I

CI CI

" / '=C/ ' ' \CH, CH,

CI

CI

I CI

II

CH, CI

" /'C= CI ' \

CI CH,

CH,CHCI,H CI

HC. C H

I i

CI

I

7. The rate equation for the decomposition of hydrogen bromide

2HBr(g) H, (g) + Br,(g)

is : Rate = k[HBr)'

Which of the following conclusions can be drawn from this information?

'" A The value of k depends on the concentration of HBr.

® The rate of appearance of Br2 is half the rate of disappearance of HBr.\( C Doubling the concentration of HBr will double the rate of reaction.

o The presence of a suitable catalyst will increase the value of k.

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CONFIDENTIAL' 8,

------ y//' - ---- x

8. In the diagram above, curve X was obtained by observing the decomposition of 100 em 3of

1.0 mol dm" hydrogen peroxide, catalysed by manganese (IV) oxide.

Which alteration to the original experimental condition would produce curve Y?A Adding water

® Adding some 0.1 mol dm" hydrogen peroxide

C Using less manganese(lV) oxide

D Lowering the temperature

9. The graph below shows the variation of pH value with volume of base added in an acid·

base titration.

,.

1312

11

10

•pH 7

6,•J

21

.L-__ - - - - - ~ - - -Volume of base addcdIcm3

Which of the following statements is not true about the mration above?

'" A The acid and base used in the titration may probably be ethanoic acid

and sodium hydroxide respectively.

v B The pK. of the acid used is equal to 4.7.

C The s a ~ formed in the titration undergoes hydrolysis to produce OH'

ions.

® A suitable indicator for the above titration is methyl orange',

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, - - - - ------CONFIDENTIAL' 10

10. The pH of a 1.0 mol dm-3 solution of a weak monobasic acid is 5. What is the

dissociation constant of the weak acid?A 1.0 x llr mol dm "

B 1.0 x 10-' mol dm"

@ 1.0 x 10., 0 mol dm,3

o 1.0 x 10". mol dm-3

11 . Hydrogen sulphide reacts with water according to the following equation.

[, ' ._ ( I

" v I i J

H,5 (aq) + 2H ,O (aq) 2H ,O' (aq) + 5 '- (aq)

Which of the following aqueous solutions when added would cause the system at

equilibrium to shift to the left?< •

A Ammonium chloride

B Sodium ~ a t e C Sodium ethanoate .

@ Ammonia

"... :

-'-'·:T ...

12. When the system CI,(g) + PCI,(g) ........ PCI,(g) is in equilibrium at 600'C, at 1

atm pressure, the value of the equilibrium constant, Kp s 30.

VVhat is the valUe of at a pressure of 2 atm at the same temperature?

.S:. A 20 ® 30 C. 60 D 100

\

13 . A solute, S exists in the same molecular state when dissolved in ether and water.

When the two solutions are in equilibrium, the concentration of solute S in ether solution is 6

times higher than that of the aqueous solution. A solution containing 14.0 9 of 5 in 240 em' of

water is extracted with 40 cm

3

of ether. Calculate the total mass of S extracted from water.A

B

©D

2.0g'J 8.6 c

'6.0g ,

,' (

7.0g

8.0 9 , "2'10 I ~ . 'I(fif?'

I; !>I = \3 >(

lL

Ilx - 14 - l (

·3>" it

{

b

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in the Fe3+

/ Fe2+

cell will increase

cell to the electrode in the

a mixture of

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CONFIDENTIAL" 14

16. In the construction of cardiac pacemakers, it is possible to use a very small magnesium,

electrode which creates an electrical cell with the inhaled oxygen. The relevant half-cells are

as follows. MS + (), -+ --r fV1g" .. t--l :z.O

Mg"+ 2 e ~ Mg E6=-2.38V p 3.25 < E _ .3!ln [ p' J I ]F - I -

C. r e C ': t .. .%02 + 2H+ + 2e EO = +1.23 V ( . « ~ -.I

Under standard conditions, the cell a.m .t would be 3.61 V, but in the body a potential of 3.25 V

is more usual. What is the best explanation of this lower a.m.f?

A The small size of the magnesium efectrode

B The low concentration of Mg2+ ions surrounding the magnesium electrode

C The high resistance of the body fluids surrounding the electrodes.

@) The pH belween 7 and 8 of the body fluid surrounding the electrodes.

17. The enthalpy change for two reactions are given by the following equations.

2Fe(s) + 'I,O,(g) Fe,O,(s);

C(s) + %O,(g) CO(g) ;

dH = - 822 kJ mor'

dH = -110 kJ mor'

What is the enthalpy change for the following reaction?

3C(s) + Fe,O,(s) 2Fe(s) + 3CO(g)

o -.2:>. 3{-lIo)

A +712 kJ m01 -'

® +492 kJ m01·'

C - 492 kJ mor'

D -712 kJ mor'

18. Which value would be required to estimate the lattice energy for the hypothetical ionic

compound. MgH?

® The electron affinity of hydrogen

B The first ionisation energy of hydrogen

C The magnesium-hydrogen bond energy

o The standard enthalpy change of formation of MgHz

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c., 1-\ I .. I 0,-

CONFIDENTIAL' .;;.

x+ \2

,_ ~ O " L ... H.O

16

19. 4.0 9 of a hydrocarbon required 16.0 9 of oxygen for complete combustion and 9.0 9 of

water was produced in the reaction. What was the mass of carbon dioxide produced?

[Relative atomic mass of 0=16, C= 12, H=lJ

A U g B Mg

@ 11 .0 9 0 22.0 9

20. The values of of several substance are given below .

Substance pI<"

NH, 4.75

CH ,NH, 3.36

CH 3CH2NH 2 3.27

CeHsNH2 9.38

Which of the following is the strongest ac id?

A NH/ B

C CH ,CH ,NH ,· ®

21. Consider the sequence of oxides given below . Which se ries shows an increasing order

of melting point?

A Ci,O" Ai,O" SO" SiO,

S S03. el 20 r• Al20]. Si0 2

® SO" Ci,o" SiO" Ai,O,

o SiO" Ai,O" CI,o" SO,

22. The process of chemical etching consists of partially dissolving a metal in a s u i t a ~ e solvent. By careful masking of the metal , it is possible to produce a pattern in or on the metal.

Which of the following aqueous solutions could be used to etch a pattern in aluminium?

A Ethanoic acid

B Dilute nitric acid Ht NO,-

@) Sodium hydroxide No' OH-0 Concentrated nitric acid

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CONFIDENTIAL' 18

23. Which of the following statements regarding lead(lV) oxide is not true?

- A It is amphoteric.., 8 It easily decomposes when heated

C It has ionic bonding with covalent characteristics.

@ It is formed by heating strongly lead (lI) oxide in oxygen

24 . Which reaction of ammonia does not involve the non·bonding pair of electrons on the

nitrogen atom?

A NH ,(g) + CH ,I(g) _ CH ,NH ; r (s)

B NH ,(g) + HCI (g) _ NH ,CI(s)

C 2NH,(I) + 2Na(s) _ 2NaNH,(s) + H,(g)

® 2NH ,(aq) + Ag'(aq) _ [Ag(NH,)'J'(aq)

25. p. Q, and R are three elements in Group 17.a is a solid at room temperature. P- ion is

the weakest reducing agent among P-, a-and R- .

26.

27.

What is the arrangement of the elements in increasing intensity of colour?

®B

C

D

P. R.Q

R.Q, P

P,Q, R

Q,R, P ,''..

A "i :

"hich of the following complexes does not exhibit optical isomerism?

A [Cr(C,O,),(H,O),f ,\

B

C

®

[Cr(C ,O,J,]>-

[ C o ( e n ) , C I ~ [Co(NH,J,(NO,) ,]

)

-... ' /

,

The intermediate species formed in the mechanism of the reaction between methaneand chlorine in the presence of light is

ACH ; B c r C CHCI ,

II

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b C C x H ~ -t . ---7 2M) CO, -r30o{-i.,O

CONFIDENTIAL· 2. '5 CH, 1 0, 20 --t ,06 COL + I I ':. I' ..O . O Q ~ ' > o. () 1«;

28. When 60 em 3 of a hydrocarbon w ere burnt completely in oxygen, 240 em 3 of carbon

dioxide and 0.0125 mol of water were produced . What is the molecular formula of the

hydrocarbon? (The volumes of aI/ gases were measured at room conditions . The molar

volume of any gas at room conditions is 24 .0 dm3

)

A C2He B C3Ha

C C3He ® C4H10

U

I

Ole - c.oo"NH.

29. Which type of isomerism is shown by each of the following organic compounds?

\..I p.

c. .,; C.,CJ,; (Y ; l lA

XB

oD

""'ok; o - s e

30. Which one of the following compounds has the highest PI<. value?

A

C

@-NH ,

CH,-N-CH,ICH,

B @-CH2NH ,

® O'N-@-NH,

31 . Lactic acid can be formed from ethanol as shown in the reaction scheme below.

OH

*p I *'PO step m IOI,CH,OH - OI,CHO--;;0;- Q 01, - f" -C = 0

OH

,Name the types of reaction that occur in step I and step III.,

Step I Step III

<A) Oxidation Hydrolysis

B Reduction Esterification

C Condensation Oxidation

0 Dehydration Condensation

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-

CONFIDENTIAL· 22

32. Which of the following compound is formed when ethanoy1 chloride is reacted with

,?O-I{_ -q

H,N - -<Q( -CH,OH

OH

A ~ H ' O C OH

@ .CH,COHN - - (c))--CH ,OCOCH,

'oCOCH ,

33. The structure of cyclohexanone is shown below.

Which statement is true about cyclohexanone?

A It is an aromatic ketone.

B tts molecular formula is CSH120 .

C It can be oxidised td benzoic acid.

® It will give a precipitate With 2,4-dinitrophenylhydrazine.

c

34. Natural rubber is a polymer made up of isoprene units with the structural formula

CH , = C(CH,)CH = CH , . Which of the following is not true about th is statement?

A The IUPAC name for isoprene is 2-methylbuta-1 ,3-diene

B Natural rubber is made from unsaturated molecules

C Natural rubber becomes hard when vulcanized

@ Natural rubber is a mixture of cis polymers and trans polymers

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CONFIDENTIAL" 24c,

35. X, Y and Z.are three different compounds . X reacts with sodium to give off hydrogen

gas . X and Y react to form an ester. X and Z also react to fonn the same ester but at a muchslower rate. Compound Y is probably X co, b 'Ej I""> r o r c ( l ' 1 ( j ~ I

A propan-1-01 y ol:. ol·c i

B propanal i'f0p"no:L© propanoic acid

D propanoyl chloride

3&. Which of the following statements is incorrect regarding the compoundge'ow? D

CH , (OH)CHCH,COCH, eLI I I ',.- 1 - ell -CH

,. C-C.I-I _I •

A It will decolourise acidified potassium manganate(VII). OH

B It can react with alkaline iodine to give a yellow precipitate.

C It is optically active.

® It will produce a brick-red precipttate with Fehling's solution.

37, When X (a gas) reacts with Y, a mixture of CH ,BrCH,Br and CH,BrCH,OH are

produced. X and Yare probably

X Y

® Ethene Brom ine water

B Ethene Sodium brom ide solutionQ. al

C HBr(g) Ethene

D Br2vapour Ethene

38. A compound Q has the following composition by mass. Carbon, 64.3% ; hydrogen,

7.1%; oxygen, 28.6%. Q reduces Fehling's solution to copper(l) oxide. 0.1 mol Q reacts with4480 em' hydrogen gas at s.t.p. with nickel as catalyst. Q is

[Relative atomic mass: H, 1; C, 12; 0 , 16. 1 mol gas occupies 22.4 dm' at s.t.p.]

@ CH, = CHCHO C CH ,CH = CHCH = CHCHO

B CH" CCH,OH D CH,COCH = CHCH = CHOH

0

C H 0 /1

5. ~ 5 8 ITiS8 C3H.O(-H

I . I

'+ \". J c,I-I.O *H. c, H, 0v·2

C,H%O,

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. /

CONFIDENTIAL' 26

39. An organic compound, W, is boiled with aqueous sodium hydroxide and the reaction

mixture is allowed to cool. Upon cooling , compound X and compound Y (an alcohol) are

produced . On acidification, compound X is converted to compound Z (C3Hs0 2) . Compound Ygives a positive triiodomethane (iodofonn) test. Compound W is likely to have the structural

formula

A CH,CH,COOCH,

B CH,COOCH ,

® CH,CH,COOCH,CH,

D CH,CH(OH)CH,COCI

40. Wh ich of the following pairs of reactants will not produce the compound with the

structural fonnula shown below.

CH ,,@ - f- cH , CH ,

c

OH

A CH,CH,MgBr and @-e0CH ,

CH,

B I and @-MgB rCH ,CH,-G=O

C @-COCH ,CH, and CH ,MgBr

,

@-cH,CH,MgBr a ~ d CH ,CHO

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CONFIDENTIAL' 28

Section B

For each question in this section, one or more of the three numbered statements 1 to 3may beCOI1>lCf. The responses A to 0 should be selected as follows:

A B C 0

1 only 1 and 2 only 2 and 3 only 1,2and3

is correct are correct are correct are correct

41 The energy-level diagram for a hydrogen atom shows several electronic transitions with

frequencies '1. '2. (). f. and 's.

v

42.

j . f,

f, f,

.

n=_n ~ 4 ,,=3

n=2

n= 1

Which of the following statements is/are true of the above diagram?

cD f. and '5 represent lines in the Balmer series.

® The lines represented by f,.'2 and'3 are non-visible.

® '3 can be used to calculate the ionisation energy of hydrogen.

r{.Gltk a L .d, ~ 1 : ' " ((Which of the following mixtures would produce a solution of pH greater than 7.

@ 25 em' of 1.0 mol dm-' NaOH(aq) and 25 em' of 1.0 mol dm- ' CH,COOH(aq) .

1-\ 2 25 em' of 1.0 mol dm-' NH,CI(aq) and 25 em' of 1.0 mol dm-' NH,(aq).

3. 25 em' of 1.0 mol dm'" NaOH and 25 em' of 1.0 mol dm'" CH,COONa.

43. Which of the following can be determined by using a mass spectrometer?

CD The relative molecular mass of an organic compound

D @ The accurate mass of a nuclide (isotope)

, 9 The proton number of an unidentified element

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CONFIDENTIAL" 30

A B C 0

1 only 1 and 2 only 2 and 3 only 1, 2 and 3

is correct are correct are correct are correct

A cell is reDresented by the cell diagram below.qoi <:c,-l.Cr(s) UC"'-(aq) II Fe"(aq), Fe'-(aq) IPt(s)

Which of the following will increase the e.m.f of the cell?

1 I ~ a s e the concentration of C,... (, - -> ( . ," ' .1 ) .. . I:: ,'<0 J<2) Decrease the concentration of Fe 2+ fr ". ..; . - ,l I n _____ .'__

@ Increase the concentration of Fe'· I ... _ ) { { IG..'1II:

45. The element X has a proton number of 25. Which of the following statements islare

true of X?

[ ) The metal X has a high density

D ® X forms coloured complex ions

® The highest oxidation number of X in its ion is "7

46. Which of the following element(s) haslhave the above arrangement of atoms in its

Gl diamond

silicon

3. boron

47. Which of tile following reagents react(s) with both benzene and methylbenzene?

(1J Chlorine gas in the presence of anhydrous aluminium chloride

( \ 2 Concentrated sulphuric acid on reflux

3 Acidified potassium manganate(VlI) on reflux

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CONFIDENTIAL" 32

A B C

1 only 1 and 2 only 2 and 3 only

is correct are correct are correct

48.CH2=CH-@ - CH , Br

What type(s)'of reaction would the above compound undergo?

(i)

IlCiJ

6)

Nucleophilic substitution

Electrophilic addijion

Free radical substitution

D

1, 2 and 3

are correct

49. A compound P decolourise bromine water and does not form a white precipitate with

ethanolic silver nitrate solution .Compound P is,(jJ

<2<-CH=CH,

CI

" 2. @-CH,CH,C I

3, CH ,=CHCH,CI

CHPH

HO--@-+- CO:;HOH

50. Which of the following statements is/are true regarding the compound above?

BIt can fOfTl'l condensation homopolymer.

It can rotate the plane of plane-polarised light.

3. 1 mol of the compound would react with sodium to produce 2 mo les

of hydrogen gas.

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, .

JABATAN PELAJARAN JOHORJA n , ~ ' " n r , , " n "IJOHORJABATAN PELAJARAN JOHORJABATAN

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.JABATAN PEL,. Two hours and thirty minutes (Dua jam tiga puluh minit) ?AN JOHOR JABATANJABATAN PEL_____ __ . _____ __ ____ . __ __ _ ____ _____ __ . _ _ __ _ __ ____ __ ___ ___ __ ___?AN JOHOR JABATAN

JABATAN PELAJARAN JOHOR JABATAN PELAJARAN JOHOR JABATAN PELAJARAN JOHOR JABATAN

JABATAN PELAJARAN JOHOR JABATAN PELAJARAN JOHOR JABATAN PELAJARAN JOHOR JABATAN

JABATAN PELAJARAN JOHOR

SI.JIL TINGGI PERSEKOLAHAN MALAYSIA

Instructions to candidates:For Examiner's use(Untuk kegunaan

Answer all the questions in Section A in the spaces provided. All pemeriksa)

working must be shown. For numerical answers, unit must be quoted 1

wherever they are appropriate. 2

Answer any four questions from section B. For this section, write 3

your answers on the answer sheets. Begin each answer on a fresh sheet 4

o fpaper and arrange your answers in numerical order. Tie your answer5

sheets to this booklet.

6

Answers may be written in either English or Malay.7

A Data Booklet is provided. 8

9

10

Total

(Jumlah)

This question paper consists of printed pages.

STPM96212

*TIris question paper is CONFIDENTIAL until the examination is over. CONFIDENTIAL·

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CONFIDENTIAL· 2

Section A [ 40 marl<s)

Answer all the questions in this section .

1. (a) Iodine, 12, crystallizes in a face-centred cubic lattice.

(i) Draw a unit cell for the iodine crystal lattice .

(ii) Calculate the number of iodine atoms in one unit cell.

[1 mark]

[1 mark]

(b) The triple point of carbon dioxide is at -57°C and 5 kPa , while its critical paint

is at 31°C and 73 kPa .

(i) Define triple point. [1 mark]

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CONFIDENTIAL 4

(ii) Sketch the phase diagram of carbon dioxide based on the information

above. [3 marks]

(iii) Based on your diagram in b(ii), explain why solid carbon dioxide sublimes at

room temperature. [1 mark]

(iv) A piece of solid carbon dioxide with a mass of 5.50 g is placed in a 10.0 dm3

vessel that already contains air at 93 .7 kPa and 24.0oC . After the carbon dioxide

has totally vaporized, calculate the total pressure in the container at 24.0oC.

[3 marks]

- - -- - -

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CONFIDENTIAL* 6

2. Consider the incomplete Born-Haber cycle and the table of data below.

I

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

,

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

,

Standard enthalpy change Value of enthalpy change/kJmor1

Enthalpy of atomization of chlorine +121

Enthalpy of atomization of calcium +178

First ionization energy of calcium +590

Second ionization energy of calcium +1145

Electron affinity of chlorine -364

Lattice energy of calcium chloride -2237

(a) Complete the Born-Haber cycle above by writing the appropriate chemical

formulae, with state symbols, on the dotted lines. [3 mar1<s]

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CONFIDENTIAL* 8

(b) Use the cycle and the values given in the table to calculate the standard

enthalpy of formation of calcium chloride. [2 marks]

(c) The standard enthalpies of hydration of theCa 2

+

and thec r

ions are-1650 kJ

mol-1and -364 kJ mor1respectively . Use this information and data from the table in

part (a) to calculate the enthalpy of solution of calcium chloride. [2 marks]

(d) The standard enthalpy of solution of ammonium chloride, NH 4CI, is

+15 kJ mor1 .

A 2.09 sample of ammonium chloride is dissolved in 50 9 of water. Both

substances are initially at 20°C.

Calculate the temperature change and the final temperature of the solution.

Assume that the specific heat capacity of the solution is 4.2 JK-19-1.

[3 marks]

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CONFIDENTIAL* 10

3. Aluminium is the first element of Group 13 in the Periodic Table.

(a) State the valence electronic configuration of aluminium [1 mark]

................. ..... ... ....................... ........... ..... ........ .... ................ .................... ...... .... ............(b) When aqueous sodium hydroxide is added to an aqueous solution of

aluminium chloride, a white precipitate, P, is formed. This precipitate dissolves in

excess sodium hydroxide, fOmling an ion, Q .

(i) Name the precipitate P. [1 mark]

(ii) What is the formula of ion Q ? [1 mark]

(c) An aqueous solution of aluminium salt is acidic.

(i) Describe what you would observe when aqueous sodium carbonate is

added to aqueous aluminium chloride. [2 marks]

(ii) Write an ionic equation for the reaction in (c) [1 mark)

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CONFIDENTIAL* 12

(d) Aluminium chloride can be used as a catalyst in Friedal Crafts alkylation of

b e n z ~ n e . (i) Write an equation for the reaction between aluminium chloride and

chloromethane to form an electrophile . [1 mark]

(ii) Use your understanding of acids and bases to explain the role of

aluminium chloride in the reaction above. [2 marks]

... ..... ..... ............. ... ... ... ..... ..... ... ............................ ...... ... ..... ...... ... ...................................(e) State one property which enables aluminium to be used in overhead electric

cables. [1 mark]

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

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CONFIDENTIAL* 14

4. (a) The diagram shows how to distinguish between propanal and propanone.

Tollen's reagent

+ propanal or

propanone - - I f - - - ,water

theat

(i) State the metal ion present in Tollen's reagent.

............... .. .... .... ... ...... .. ........ .... .. ... .... ........ .... .. .. ............... .. ........... ... .... .. ... ..... ...[1 mark]

(ii) State the functional group present in both propanal and propanone

... ............................ ......... ..... .. ... ... .. ....... ... .......... ........... ............ ... ................... [1 mark]

(iii) Explain why hot water is used .

.. ..... ................................. ..... .... ... .. .... ... ... ......... ......... ......... .. .. ..... .... ... .. ... .... .... [1 mark]

(iv) State what is observed in separate experiments with propanal and

propanone.

Propanal........................................................................................................

............................................. ......... .. .. .... ....... ....... ....... ...... ...... ....... ... .. .... . [1 mark)

Propanone.... .. .... ... ....... .. ..... .. ... ...... ........ ..... ......... .... .. .... .. ..... .......... .... ... .. .... .

............................................................................. ... ... ......... ..... ... .... ..... . [1 mark)

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CONFIDENTIAL· 16

(b) Adrenaline is a hormone that acts as a stimulant. It has the structural formula

shown below.

H IH ~ f , - H HO HO H CH

3

(i) State the type of isomerism that can exist in the adrenaline molecule.

[1 mark]

(ii) Draw the structural formula of the product formed when adrenaline reacts

with

NaOH (aq ) Dilute HCI

Structural formula Structural formula

[2 marks]

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CONFIDENTIAL* 18

(c) Adrenaline can be synthesized from X via the following steps:

HO

(X)

HCN

- - + ~ p

step 1

L i A I ~

- - - - ~ Qstep 2

(i) State the type of reaction that is involved in step 1

(ii) State the condition(s) required for step 2.

adrenaline

[1 mark]

[1 mark]

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CONFIDENTIAL* 20

Section B [60 marks]

Answer any four questions in this section.

5. (a) The equation below shows the reaction between ammonia and a hydrogen

ion.

In tenns of the electrons involved, explain how the bond between the NH3

molecule and the H+ ions is fonned.

Name the type of bond fonned in this reaction. [3mari<s]

(b) Boiling point data for three hydrides are given in the table below.

Hydride Relative molecular mass, M, Bolling pOint! °c

Methane 16 -182

Ammonia 17 - 33

Water 18 100

Explain why these three hydrides have very different boiling points.

[4 marks]

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CONFIDENTIAL* 22

(c) (i) A reaction of nitrogen monoxide is shown below.

The rate of reaction can be found by measuring the concentration of N02

at different times.

Define the term rate of reaction.

Sketch a graph to show how the concentration of N02 changes with time.

Indicate how the initial rate of reaction could be obtained from your graph.

[4 marks]

(ii) In the manufacture of sulphur trioxide from sulphur dioxide, nitrogen

monoxide can be used in a two-stage process to increase the rate of

production.

Construct an overall equation for the production of S03 from S02.State and explain fully the role of NO in this process.

[4 marks]

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CONFIDENTIAL* 24

6. (a) (i) Using a solution of ammonium chloride and ammonia as example, explain

what is meant by a buf fer solution. [5 marks]

(ii) Calculate the mass of ammonium chloride that needs to be added to 450

cm3of 0.10 mol dm·3ammonia to produce a solution with pH = 9.0

[1<1) of NH3 = 1.7 X 10-5 mol dm-3] [4 marks]

(b) The pK. values of four carboxylic acids are listed in the table below.

Acid Formula of acid pI<.

1 CH3CH2COOH 4.9

2. CH3CHCIC02H 2.8

3 CH3CCI2COOH 1.4

4 CH2CICH2COOH 4.1

(i) Describe and explain the trend in acidic strength shown by acids 1, 2 and

3.

(ii) Give an explanation for the difference in the pKa values for acids 2 and 4.

(iii) Calculate the pH of a 0.010 mol dm-3solution of propanoic acid (acid 1).

[6 marks]

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CONFIDENTIAL 26

7. (a) (i) State the trend in the reducing ability of the halide ions from fluoride to

iodide.

[1 mark)

(ii) State what you would observe when chlorine water reacts with a

solution of potassium iodide. Write an equation for the reaction.

State the role of chlorine in the reaction.

[3 marks)

(iii) Give a reagent which could be used to distinguish between separate

solutions of potassium bromide and potassium iodide. State what would be

observed when this reagent is added to each of the separate solutions of

potassium bromide and potassium iodide. Write an equation for one of the

reactions.

Identify a reagent which could be added to the mixtures from the first test

to confirm the identity of the halide ions. State what would be observed in

each case.

[6 marks]

(b) Carbon tetrachloride and silicon tetrachloride behave in different ways when

added to water. State how each chloride behaves and explain the difference.

[5 marks]

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CONFIDENTIAL* 28

8. (a) An aqueous solution of magnesium nitrate and barium nitrate can be

differentiated by the addition of dilute sulphuric acid.State what you would observe when the above reaction is carried out.

[3 marks]

(b) Compare and explain the solubility in water, for the solid sulphates formed in

8(a). [7 marks]

(c) The solubili ty product, Ksp, of magnesium hydroxide has a numerical value of

2.0)( 10-11 •

(i) Write an expression for the Ksp of magnesium hydroxide, stating its units.

(ii) Use the value of Ksp given to calculate the concentration of Mg(OH)2 in a

saturated solution.

(iii) Explain whether magnesium hydroxide would be more soluble or lesssoluble in 0.1 mol dm-3 MgS04(aq) than in water.

[5 marks]

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CONFIDENTIAL· 30

9. (a) (i) Write the mechanism of the reaction when 1-chloropropane is refluxed with

aqueous sodium hydroxide. Name of the type of reaction involved [3 marks]

(ii) State and explain how the rate of this reaction changes when

1-chloropropane is replaced by 1-bromopropane. [3 marks]

(iii) Write equations to show how you would change 1-chloropropane to

2-chloropropane [5 marks]

(b) The amino acids alanine and serine are shown below.

H

IH2N-C--cOOH

ICH3

alanine

H

IH2N-C--cOOH

ICH20H

senne

(i) Draw the structures of the two dipeptides formed by the reaction of

alanIne with serine.

(ii) Name one of the dipeptides formed in b(i).

(iii) Draw the structure of the organic compound formed when one molecule

of serine reacts with two molecules of ethanoyl chloride. [4 marks]

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CONFIDENTIAL 32

10. Five organic compounds, A to E, has the molecular formula CSH100.

Compounds A, Band C can react with 2,4-dinitrophenylhydrazine, but not with

Fehling's solution. Only A and B gives a positive iodoform test. A has a higher

boiling point than B .

Compounds D and E give a brick red precipitate, P , with Fehling's solution.

D is optically active. Reduction of E gives a straight chain compound, F.

Based on the information above, identify compounds A to F. Give reasons

for your choice.

Name compound P.

Write any three chemical equations for the reactions above, involving

different reagents.

[15 marks]

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Question 1(a) (i)

00

(ii) (8X2X1/8) + (6X2X112) =8

(1 )

(1 )

(b) (i) A set of temperature and pressure values where solid, liquid and gas exist in

equilibrium.

(ii)

liquid

.cUd

5 , . . ______ __ _______L---

0",

!r

,

_ ._.._- ---.--- :r, '. ...._- --," .._..._-_ . ...- 31 "" - -

General sketch of graph .

The correct axes.

The labellings.

(1 )

(1 )

(1 )

(1 )

(iii) because its triple pOint occurs at a pressure above the normal atmospheric

pressure. (1 )

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p

p =5.50 x 8.31 x (24.0+273) x 10-3 kPa

10.0 x10-3X 44.0

= 30.9 kPa

PI = 30.9 + 93.7 = 124.6 kPa

Question 2

(1 )

(1 )

(1 )

Total: 10 marks

(a) Ca2+(g) + 2e- + 2CI(g) (This is the only answer for the top line) (1)

Ca2+(g) + 2e- + CI2(g) (1)

Ca+ (g) + e- + CI2 (g) (1)

Ca(g) + CI2(g) (state symbols and electrons essential) (1)

Note: CI2to 2CI can be in any order but Ca must be in sequence)

Max. 3 marks

(b) Enthalpy of formation = 178 + 590 + 1145 + (2 x 121) - (2 x 364) - 2237 (1)

= - 810 kJ mor1

(1)

(c) flH = flH(lattice formation) + :LflH(hydration) (1)

(or cycle with state symbols, numbers or labels)

=2237 -1650 - (2 x 364)

= 141 kJ mor1

(1)

(d) Moles of NH4CI = 2153.5 = 0.0374

Heat absorbed = 15 x 0.0374 = 0.561 (1)

Q=mcf lT

f lT= Qlmc = 0.561x1000)/(50x4.2) =2.6 (0C) (1)

(allow 2.5 to 2.7; can use 52; ignore units, answer must be at least 2 sig figs)

Final temperature = 20 - 2.6 = 17.4 °c (1)

(Answer is for 20 - previous ans; must be < 20)

Note; may not use moles (loses first 2 marks)

so f lT= 15x1000)/(50x4.2)

So answers of 71.4 and 68.7 score last 2 out of first 4.

(allow no units for temperature, penalise wrong units)

Total: 10 marks

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Question 3

(a) 3s2 3p1

(b) (i) aluminium hydroxide

(ii) AI(OH)4 -

(c) (i) white precipitate

Effervescence

(ii) AI(H20)6 ]3+ + H20 _ AI(H20)s(OH)f+

(d) (i) AICh + CH3CI

(ii) as lewis acid

(1 )

(1 )

(1 )

(1)

(1)

(1 )

(1 )

(1 )

In AICI3 ,AI has an incomplete octet and accepts a pair of electrons from the CI

atom in CH 3CI @ AICh is an electron-deficient compound. and acts as an

electron-pair acceptor.

(e) light

Question 4

(a) (i) Ag+/silver

(1 )

(1 )

Total = 10 marks

(1 )

(ii) Carbonyl or C =0 (1)

(iii) Helps to speed up the reaction/slow at room temperaturelflammable (1)

(iv) Propanal: silver mirror formed

Propanone: no change/solution remains colourless

(b) (i) optical isomerism

(ii)(a)

(13)

H rN a ( } - -

Hb H cH,

(c) (i) nucleophilic addition

(ii) dry ether, room temperature

(1 )

(1 )

(1 )

(1 )

(1 )

(1 )

(1 )

Total = 10 marks

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r

Question 5

(a) Lone pair donated / both electrons supplied by one atom

from N (to W) [ignore missing charge or hydrogen atom)

dative/dative covalent/coordinate bonding

(b) Van der Waals ( or VrNV) forces between methane molecules

(or VdW forces in methane)

Hydrogen bonding in ammonia and water

Hydrogen bonds are stronger than van der Waals forces

( orVdW forces are the weakest)

(1 )

(1)

(1 )

(1)

(1 )

(1)

Hydrogen bonds in water more extensive than ammonia because 0 has two lone

pairs (N one) (1 )

[or Water forms more H bonds per molecule (than ammonia»)

(or H bonds in water stronger because 0 more electronegative than N)

(or H bonds in water stronger because 0 - H bond more polar than N - H)

(c) (i) The change in concentration per unit of time (1)

Both axes must be labelled to gain marks for graph. y axis cone N02and x axis time (1)

Curve starts at origin and levels off. (1)

Note: If candidates graph does not level off then second mark can be scored for a

CUNe with a continuously decreasing gradient.

Initial rate can be found by finding the gradient at t = 0 (1)

Note: Candidates may score this mark if they have shown this on their graph

NO is a catalyst

it is regenerated at the end of the reaction

provides an alternative route of lower activation energy

(1 )

(1)

(1 )

(1)

Total = 5 marks

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- -_ . -.- - .

--

Question 6

(a) (i) A buffer solution has the ability to resist changes in pH when a little acid or base is

added .

When a little acid is added, it reacts with NH3 . The acid is used up, pH remains

unchanged

NH3 + H+ NH/

(1 )

(1 )

(1 )

When a little base is added, it reacts with OW The base is used up, pH remains

unchanged

NH/ + OH-

(ii) pOH = 14.0 - 9.0 = 5.0

QIU .v I [NH;1p L1 =Pf tb + og [NH,J

5.0 = log1.7x10-5 + log [NH/] 10.10

[NH/] =0.17 mol dm-3

mass of NH4CI in 450 cm3=0.17 x 53.5 x 450/1000 = 4.1 g

(b) (i) acid strength increases from no. 1 to no. 3 or

down the table or

(1)

(1)

(1 )

(1 )

(1)

(1 )

as number of CI increase (1)

due to the electron-withdrawing effect or

electronegativity of chlorine (atoms) (1)

stabilising the anion or weakening the O-H bond (1)

NOT H+ more available

(ii) chlorine atom is further away (from O-H) in no. 4, so has less influence (1)

(iii) either: pH = pKa - IOg10 [acid) or Ka = 10 - pKa = 1.259 x 10-3

= 4.9 + 2) [H+) = (Ka. c) = .55 x 10"" (1)

'"' 3.4 (allow 3.5) pH =3.4 (1)

Note: [1) for correct expression & values;

[1] for correct working

Total = 5 marks

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Question 7

(a) (i) Increase (1)

(ii) Colourless solution tums to a brown solutionl black ppt

(need both colours) (1)CI2 + 2KI 12 + 2 KCI (1)

CI 2 is an oxidising agent (1)

(iii) Add silver nitrate solution (1 )

KBr forms creamy ppt (1)

KI forms yellow ppt (1)

AgN03+ KBr AgBr + KN03 or

AgN03 + KI Agi + KN03 (1)

or ionic equations

Then add (dilute or conc) ammonia (1)

AgBr/ cream ppt dissolves in conc NH3 or

slightly dissolves in dilute NH3 (1)

Agi is insoluble in dilute or conc NH3 (1)

(b) SiCl, reacts/hydrolyses, CCl, does not (1)

[This must be clearly stated and not just implied]

(lone) pair of electrons (from the oxygen atom) in a water molecule (1)

cannot form a bond with/be donated to the C atomOr cannot be accepted by C atom (1)

because C has no available orbital

OR no 3d orbitals in C

OR C is a small atom surrounded by CI atoms

OR CI atoms are large and surround C atom (so attack is sterically hindered) (1)

Rejects CCI4 has no d orbitals

Si has (available) 3d orbitals (1 )

Rejects SiCI4 has available 3d orbitals

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Question 8

(a) white precipitate formed fo r barium nitrate

no visible change for magnesium nitrate

H2S04(aq) + Ba(N03h --. ..

Ba2+(aq) + SO/-(aq)

BaS04(s) + 2HN03(aq) @

BaS04(s)

(1)

(1 )

(1 )

(b) ionic size of Mg2+ < Ba2+ (1)

magnitude of hydration energy of Mg2+ » 8a2+ (1)

ionic size of sol-» size of cations Mg2+ and 8a2+ (1)

magnitude of lattice energy for MgS04 slightly more than 8aS04 (1)

LiHsolution= LiHhydration -LiH lattice (1 )

For MgS04 •LiHsolution= xothermic; For BaS04 • LiHsolution= ndothennic ; (1)

barium sulphate - inscluble in water; magnesium sulphate - soluble (1)

(c) (i) (Ksp =) [Mg2+][OH1

2(1)

units are mol3dm-

9 (1)

(ii) Let [Mg(OHh(aq)) =Mg2+] =Ksp = X 10-11 = x3 (1)x =1_71 X 10-4 mol dm-

3 (1)

(iii) less soluble because of the common ion effect

or the equilibrium Mg(OHh(s) --> Mg2+(aq) + 20W(aq) is moved to the left

(1 )

Total = 15 marks

to

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Question 10

They don't react with Fehling's solution - they are ketones (1)

A and B gives positive iodoform test - they have the structureCH3 C = 0 or methylketone (1)

I

Boiling point of A> B - A is less branched compared to B (1)

A is CH3COCH2CH2CH3 (1)

o and E gives a positive test with Fehling's solution - they are aldehydes (1)

o s optically active. Hence isomers of 0 are

Reduction of E gives a long chain compound, F

E is CH3CH 2CH 2CH 2CHO

F is CH3CH2CH2CH2CH20H

Pis copper(l) oxide (reject CU20)

Examples of equations:

«H3CH

3CH

2CH

2C=O + H2NNH- - \Q,>-- N02 --_

(2)

(1 )

(1 )

(1 )

(3)

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stpm trial 2009 che q&a (johor)

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