johor stpm trial 2011 chemistry paper 2(no bahasa melayu slide) and answer

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JABATAN PELAJARAN JOHOR

SIJIL TINGGI PERSEKOLAHAN MALAYSIA

Instructions to candidates:

Answer illthe questions in Section A in the spaces provided. Allworking must 6e shown. For numerical answers, znil must be quotedwherever they are appropriate.

Answer any four questionsfrom section B. For this section, writeyour answers on the answer sheets. Begin each answer on afresh sheetof paper and arrange your answers in numerical orfur. Tie your answersheets to this booklet.

Answers may be written in either English or Malay.

A Data BooHet is provided

For Examiner's use(Untuk kegunaan

pemeriksa)

I

2

3

4

5

6

7

8

9

l0

Total

(Jumlah)

This question paper consists of 23 printed pages.

STPM 96212*This question paper is CONFIDENTIA! until the examination is over. CONFIDENTIAL*

http://edu.joshuatly.com/

CONFIDENTIAL* 2

Section A [40 marksl

Answer all the questions in this section.

1. (a) A 20 dm3 closed vessel containing 1.5 mole H2g?s, x mole N2 gas and 1.2 mole CO2

gas has a total pressure of 500 kPa at a temperature of 298 K.

(i) Calculate the value of x. [3 marks]

(ii) 1.5 mole of neon gas was added into the 20 dm3 vesset. Calculate the

partial pressure of the hldrogen gas. [1 mark]

(b) Hydrazine, NzHr is used as fuel for rocket .

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

(ii) Draw the dot -cross structure for hydrazine molecule. [1 mark]

(c) The boiling point of dimethyl ether(CHsOCHs) is lower than that of propanone

(cH3cocH3).(i) Give a reason for the difference in their boiling points. [2 marks]


CONFIDENTIAL*

(ii) State the types of hybridisation present in the carbon atoms of the twocompounds below. [2 marks]

Dimethylether :

Propanone :

2 (a) (i) Give the definition for standard electrode potential. [2marks]

The standard reduction electrode potentialfor several half-cell reactions at298 K areshown in the table below.

Half-cell reactions. E0

SzOot- + 2e -+ 2SO42- +2.01

lFe(CN)el" ' + e -[Fe(CN)5]a-

+0.36

Fe"* + g-

Fgt* +0.77

12 + 2e-

2l' +0.54

When an aqueous solution of potassium peroxodisulphate , K2 S2Os is added to anaqueous solution of potassium iodide, Kl , a reddish brown solution is obtained.

(iD Write a balanced ionic equation for the above reaction. [2marks]

(iii) Write a cell diagram for the above reaction. [1mark]


I

CONFIDENTIAL*

(iv) Calculate the standard cell e.m.f. , Eo en for the reaction in (b)(iii). [1mark]

(b) The phase diagram of a substance W is shown below.

Pressure(atm)

Temperaturefc)

(i) State all the changes of phases of substance W at the following points as thetemperature increases.

P: . . . . . .

R: . . . . . .

T: . . . . . .

[2marks]

(ii) Base on the curve oY, compare the density of solid w and liquid w. [1mark]

Q:

S:

(iii) Describe the change in melting point when pressure is increased [1mark]


CONFIDENTIAL-

3 A student examined the water from a mining pool which contains lead(ll) ions. Thepresence of lead ions can be shown by the precipitation of yellow lead (ll) iodide. Thesolubility of a saturated solution of tead(ll) iodide at 15"C is 0.46 gdm-t.

(a) (i) Write an expression for the solubility product, Kp, for lead (ll) iodide at 15 oC.

[1mark]

(ii) Calculate the concentration of lead (ll) ions in moldm'3 [2marks]

(iii) Calculate the concentration of iodide ions in moldm-3. [2marks]

(iv) Calculate the solubility product, K.o, for lead (ll) iodide. Ilmarkl

(b) Strips of copper are dropped into a conical flask containing hot 507o nitric acid solution.

A colourless and very reactive gas is given off. The gas then reacts with oxygen in the air

to form a brown gas.

(i) Name the colourless gas . [1 markl

(ii) Write the equation forthe reaction between copper and nitric acid. [1 mark]

(iii) ldentify the brown gas and write an equation for its formation [2marks]


CONFIDENTIAL*

4. Pethidine is a powerful painkilling drug:

CHz

c

co2cH2cH3

10

CHsIIN:

, / \CHZ CHZ

CH.

II*Nl- cr H

. / \CHZ CHZ

CH,

c02cH2cH3

Pethidine E

(a) The pethidine molecule contains two functional groups, one which reacts with dilute

hydrochloric acid to give compound E.

(i) What type of reaction is this and what type of functional group does it show the

pethidine molecule to have? [2marks]

(ii) Name the other functional group in the molecule. State the type of reaction

undergone, and give the structural formula of each of the products, when

pethidine reacts under reflux with aqueous sodium hydroxide.

[3marks]

Functional group : ......

Type of reaction : ......

Structuralformula :

o


CONFIDENTIAL* 12

j (b) 2-bromobutane reacts with aqueous hydroxide ions to give butan-2-ol.r (D State the condition for this reaction. [1 markl

i: l : ....li fii) State what type of mechanism is involved in this reaction. [1 mark]ilI

(iiD State the reagents needed to convert 2-bromobutane to

CH3CH2CH(CH3)CH(OH)CH3 in two steps. 12 marksl

Step 1 : . . . . . . . .

Step 2 : . . . . . .

(iv) Name one reagent that can be used to differentiate between 2-bromobutane

and CHgCH2CH(CH3)CH(OH)CH3 without heating. [1 mark]


I'

CONFIDENTIAL*

Section B [60 marks]

Answertour questions in fhis section.

5. (a) The major buffer system that is used to controlthe pH of blood consists of carbonic

acid, HzCOg and sodium hydrogen carbonate, NaHCOe. Explain how the system works in

controlling the pH of the blood. [4 marks]

(b) 20.0 cm3 of 0.20 mol dm-3 aqueous NHg was titrated with 0.16 mol dm-3 aqueous

HCl. Sketch a graph of pH against volume of HCI(aq) added during the titration process.

Mark and explain the position of the equivalence point. [4 marks]

(c) The activation energy, E", of a reaction can be calculated from the Arrhenius

equat ion: k _ 1"-E, lRT

wherek=rateconstant, f t=gdsconstant,T=temperature,andA=frequencyfactor.

Rate constants for the decomposition of acetonedicarboxylic acid are k = 4.75 x 10{ s'1 at

293 K and k = 1 .63 x 10 3- s-1 at 303 K.

14

(D(ii)

(iiD

CO(CH2COOH)z (aq) # CO(CHs)z(aq) +2 COz(g)

Calculate the activation energy, E" , of this reaction.

Write the rate equation for the reaction.[4 marks]

[1 mark]

What is the time taken for the concentration of CO(CH2COOH)z (aq)

to change from 2.00 mol dm'3 to 1.00 mol dm-3 at 303 K. [2 marks]

6. (a) The following data are found of chlorine.

Enthalpy change of atomisation, AHr = +121kJ mol-1

Electron affinity, AH2 = - 364 kJ mo'1

Enthalpy change of hydration, AH3 = - 381 kJ mol'1

By drawing an energy cycle, calculate the enthalpy change for the reaction, AH4.

% Clzt.g) + water + €- € Cl- (aq) AH+.

Deduce the strength of chlorine as an oxidising agent based on the AHr value obtained.

[6 marks]


CONFIDENTIAT

(b) (i) Gases can only be liquefied by pressure alone if their temperature is below their

'critical temperature', T". Above the criticaltemperature no amount of pressure will liquefy a

gas.

Use the following data and suggest an explanation for their criticaltemperatures.

Gas formula M, T"/ocMethane

Ammonia

steam

CHo

NHs

Hzo

16

17

18

-82133

374

[5 marks]

(ii) In the industrial liquefaction of air, high pressure air is allowed to expand into a

region of low pressure, whereupon its temperature drops by a large amount. An ideal gas

does not show this behaviour. Give an explanation for the above observation.

[4 marks]

7 The formation of magnesium oxide can be represented with a Born-Haber cycle asshown below.

Md-(sl r 0r3-{g)

16

J*Ms(g)

f*Ms(s)

J*,Mg(s)

tIn ' ,olsl

A

I an,

o(g)A

I ar.

* o,,o

(a) (i) Name the enthalpy change AHr, AHz and AHz [3marks]


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epxo unrseu6eu JoJ ellq/n ',-lou rI zgre- sl epxo urnueq lo; fiblaua eclgel eqr(!!l)

[syeug],Joul P|6880 - =

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,-lou fl09l+ =

Jol 'rHV ' uollewrolJo eOueqc r{dleq1ue eql elelnclec'elep 6u;mo11ol eql uot3 (g;)

,HV

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8t*'lvtlN30lJNoc


CONFIDENTIAL-

9. (a) Explain the term optical isomerism, using the compound CHaCH(OH)CH2CH3 8s ?rl

example. [3 marks]

(b ) X, C8H10O , liberates white fumes with phosphorous(V) chloride. X reacts with alkaline

iodine to give yellow precipitates. When X is heated with an excess of concentrated

sulphuric acid, compound Y is formed. Y can be converted to X. Under suitable conditions ,

Y undergoes polYmerization.

Determine the structure of X and Y. Explain how you derive the structures and write the

Equations of the reactions involved. [Tmarks]

(c) Compounds A and B are two isomers with molecular formula CaHroO. A dissolves in

aqueous sodium hydroxide but B does not. B gives off white fumes with thionyl chloride and

forms a yellow precipitate with alkaline aqueous iodine but A does not. B is synthesised

starting from bromobenzene whereas A is from 4-ethylaniline.

Explain the above observations and write the structural formulae of A and B. [5 marks]

10. (a) Compounds R and S have the following structure.

@"HzCHzNHz @"t2coNH2RS

(i) Write equations for the reac,tions, if any, when R and S react separately with

dilute hydrochloric acid under suitable conditions. [2 marks]

(ii) Describe briefly a chemicaltest, stating the reagents and conditions used, and

observations, to distinguish between R and S. [3 rnarks]

20


CONFIDENTIAL* 22

(b) State the reagents and conditions for steps | , ll and lll. Draw the structural fonnulae ofA and B.

CH3CH2CH2BT $ g II, CH*CHaCHaCOTH

I I I

Bf CHsCHzCTCO2CI

Qlo*[5marksl

(c) Describe the scheme of reactions(in not more than 3 steps), slating the reagents andconditions, forthe synthesis

" @cooc2H' starting rrom@Lr. .

[S marks]


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JABATAN PELAJARAN JOHOR

SIJIL TINGGI PERSEKOLAHAN MALAYSIA

STPM 96211

CONT'IDENTI.A,L*http://edu.joshuatly.com/

ANSWER FOR CHEMISTRY PAPER 1 (TRIAL EXAM} 2011

1 D 11 D 21 c 31 B 41 G

2 A 12 D 22 D 32 A 42 c3 D 13 B 23 B 33 B 43 A4 A 14 D 24 A 34 c 44 B5 A 15 c 25 D 35 c 45 D6 B 16 c 26 B 36 A 46 B7 c 17 A 27 D 37 B 47 B8 c 18 B 28 B 38 D 48 D9 A 19 G 29 B 39 D 49 B

10 B 20 B 30 c 40 c 50 B

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Question Details Mark Awarded

1(a)(i)

1(a)(ii)

PV = nRT

500 x 103x 20.0 x 10-3 = (1.5 + x + 1,2) x 8.31 x 29gX= 1.3Or

. . 500x 103x 20.0 x 10-3x= - 2.7

1.5

8.31 x 298

1.3

x500=l88kPa1.5 + I .3+1.2

1

1

1

1(bxi)

1(bxiD

N: 1s22s22p3

xx +*

Ho*lx ** IJ*

ot

HH

1(c)(i)

1(c)(ii)

Relative molecular mass of propanone is higher, thereforestronger Van der Waals forces of attractions exist betweenmolecules compared to the ether.

Ether: sp3

Propanone:spt,sp'



2(a) (i)

2(a) (ii)

2(a) (iii)

2(a) (iv)

The standard electrode potentialis the potential differencebetween the standard hydrogen electrode and otherelectrode systems with the concentration of 1.0 M at tatm / under standard conditions

SrOu t- 2e

2l

-->

---+

2SOot-

la+2e

Sror'- 2r 2SOot-

Pt(s)/ l - (aq), lz(aq) SrOu o (aq) , SOa2- (aq) / pt(s)

E@ .ur = +2-A1V-(+0.54V)=+1.47Y

2 (b) (i)

2 (b) (ii)

2 (b) (iiD

PS

solidliquid & gas

Q: solid &liquid R: liquidT: Gas

Density of solid W is lower than liquid W.

The melting point decrease with increase in pressure

4-5 correct:2m

2-3 correct:1m


3 (a) (i)

3 (a) (ii)

3 (a) (iii)

3 (a) (iii)

K.p = [ pb'z.]lll

R.M.M of Pbl2 = 461,

concentration of Pbl2 in water =0.46 g dm-.The concentration of the lead ion = 0.46t461

= 9.978 X 104 moldm-3=10.0 X 10-4 mol dm-3

The concentration of the iodide ion = 2 X I pbr.J

=2X9.978X10-4

., . , , : . . = 1.996X 103moldm-3= 2.e X 10 3 mol dm-3

K"p = [Pbr.][r],=[9.978 X 104 ] l 1.996 X 10-.12= 3.975 X 10-e mol3dm-e= 4.0 X 10-e mol tdm-9,

3 (b) (i)

3 (b) (ii)

3 (b) (iii)

Nitrogen monoxide gas, NO

3Cu1"y + 8HNO31"qy -'3Cu(NO3)21"01

Brown gas : nitrogen dioxide,NO22NQnl + Oe{s)e 2NO4e1Colourless Brown

+ 2NO (e) + 4HzOo)



aa(i')

('i)I

Acid-base reactionAmine functional group

Functionaf group : Ester

Type of reaction : hydrolysis

Structural Formula:

CHrII

N:

CHz

III

C\C

CHz

II

rts,

COO- Na* c2H5oH

4(b) (i)

(iD

(iiD

(iv)

Reflux

Nucleophilic substitution

Step 1 - magnesium and dry ether

Step 2 - CH3CHO followed by dilute acid

Sodium / PCls / SOCI2 / PCl3


Question Details Mark Awarded5(a) H2CO3(aq) <-----+ HCO3 (aq) + H*(aq)

In the presence of acid,HCO3-(aq) + H"(aq) r-------> HzCOg(aq)

Carbonic acid being unstable, decompose to CO2 and H2OIn the presence of alkali,llzcor(aa) + oH-(aq) r--> HCo:-(ad + Hro(l)

5(b)

ltrlurn* of fi{} rnl$c.ljern'

Hydrolysis of NHa* ions in water, thus is acidic

NHo* + 11rg <-> NH, + 1-1rg* pH<7

Equivalence point

i 1,0 ll :'s !r -t0 j5 ;hl ,i5

Shape -1m

Label - 1m

End point <7 -1m

5(c) (i)

(ii)

(iii)

E rl)fsk=rgA- #r*f , I

E 9: =!:-(f -1] unsubstituted- k2 2.303R\72 \ )

Substituting kr = 1.63 x 10-3 , T1 = 303 substitutedkz= 4.75 x 10-a ,T2= 2g3E"= 9.10 x 104 J or 91.0 kJRate = k[CO(CHTCOOH)r] 1

0.693llme = ___;

1.63x10-'= 425s

11


Details

%.ch(o) --ll3l-+ct1g1

l r^rL I l-ta+

JICr(aq) ( -38r cr(g)

AHa = +121+(- 364) +1-381)= 121-364-381= 424 kJ

AHa very exothermic,

4 correct:2 m3 correct: 1 m

6(bxi)Criticaltemperature of CH+ < NHe < HzO

- CHo has weak Van der Waals forces of attraction betweenmolecules,

- NH. and steam has strong H-bonding

- H-bonding in water is stronger than in ammonia

- the stronger the intermolecular forces of attraction , the moregnergy is required to overcome them, thus the criticaltemperature

-Energy is required to overcome the intermolecular forces ofattraction.

- energy is drawn from the surroundings, temperature drop

-ideal gas has negligibre intermolecular forces of attraction

- expansion of idealgas does not require energy to overcome theintermolecular forces of attraction



(ii)

7(a)(i)

(iii)

AHt = Atomisation enthalpy of magnesium

LHz = First ionisation energy of magnesium

AH7 = Lattice energy of magnesium oxide

AHr =AHr +AHz +AHs +AHq +AHs +AHo + AHz

= +150+(+ 736)+1 + 1450)+(+ 950) +(-3389)

= - 603 kJ/mof

The charge of Mg 2* ion and Ba 2* ion are the same but the size of theMg '* ion is smaller compared to the Ba 2* ion

Lattice energy = QrQ.r* *[-

So, Lattice energy of MgO > BaO

I

I

I

I

I

I

I

I

b(D - CFCs can cause depletion of ozone layer- because they are unreactive

fnitiation step: CCI2F, 2> . CCIFz + o Cl

Propagation step : o Cl + O. -+ ClOo + Oz

Net reaction: 2Qt

ClOo +O -> oCl+Oz

-----+ 3O2

(ii) Hydrofluorocarbon, HFC

will not release damaging chlorine free radicals into the atmosphereORC-H bonds will br-eak down before they reach stratosphere



8(aXi)

8(a)(ii)

With cold NaOH(aq)

-C hl ori ne u ndegoes disproporti onation' reaction i n coldNaOH(aq) to form NaCland NaClO.0-1 +1Cl2 + 2NaOH > N*l +NaClO +HzO

-Chlorine oxidised to NaCIO and reducedto NaCl.The NaCland NaCIO produced are sodium salts and have no chlorinesmell.

With hot NaOH(aq)-Chlorine undegoes disproportionation reaction in hotNaOH(aq) to form NaCl and NaClOs.0-1 +53Cl2 + 6NaOH ) SNaCl +NaClOs +3HzO

Chlorine oxidised to NaClOs and reduced to NaCl.The NaCland NaClO. produced are sodium salts and have nochlorine smell.

- Fluorine is highly electronegative element.HF has thehighest b.p because hydrogen bonding exist between HFmolecules.

- Hydrogen bonding does not exist in HCl,HBr and Hlbecause Cl, Br and I atoms are not highlyelectronegative.

- b.p increases from HGlto Hl because the molecular sizeincreases from HCI to Hl.

-The larger the molecular size, the stronger the Van derWaals forces of attraction between the molecules andthe higher the b.p.

I

I

I

(max 5m)

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I

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e(a) Optical isomerism occurs in compounds with the samestructural formula but differ in their effect on plan+polarisedlight.

- Opticd isomers contain a chiral carbon,

- Are nonsuperimposable or minor images to one another,

1

(max 3 marks)

- Rotate the plane of plane'polarised light in oppositedirection but to the same degree.Eg

oHI

cH. - c'- cH2cH3IH

(b)Since X gives white fumes with.fQlq, { is an alcohol.

X gives a give yellow precipitates with alkaline iodine showsthat X has structure . CH3CH(OH)R

Hence X is 1-phenvlethanol. CHsCH(OH)CoH,L

Equations:

CH3CH(OH)CoHs + PCls -> CH3CH(CI)CoHs +

x HCI + POCIrWhite fumes

CH3CH(OH)CoHs +X

4Iz + 6Na OH- ----+ CHI3 +yellow precipitate

CoHsCOO-Na +5NaI+5HzO

Excess H2SO4CHz= CH (C6Hs) +

Y HzOCH3CH(OH)CeHs

X

X undergo dehydration to form Y, phenylethgne,

CHe:CHCoHr

I

I

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(7)


(c) - A and B are aromatic compounds, highly unsaturated

-Aisaphenol

- B contains -OH group and the structure

OHI

cH3-c-IH

- 4-ethylaniline reacts with nitrous acid to produce A

- bromobenzene reacts with Mg/dry ether to produce a

Grignard reagent. The Grignard reagent then reacts with

ethanalto produce a 20 alcohol, BOH

ICHCH:

A: B:

cH2cH3

1

1


Question

10(a)(i)

Details MarkAwarded

,r;<\\!2/"t2cH2NH2

+ Hcl H2CH2NH3*Cl-

@"n2coNHz + Hct+ Hzo-@cH2cooH

+ NH4cr

1

1

(ii)

10(b)

Reagents used - sodium hydroxide lConditions - reflux fObservations -

R - no visible reaction

S - gas with a characteristic smell, NH. , given off .

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1

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Step l- KCN / ethanol, reflux

Step ll- HCl, reflux

Step lll - PCls or SOCIz

A: CH3CHzCH2CN

B:

o-c-cH2cH2cH3

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10(c)

@*. ooH

IlCzHsOH /lConc H2SO4 ,lrefluxI

7.1t

\!,lcooc2Hs

Step 1 - oxidation of methylbenzene

Reagent- KMnOr and H2SOaCondition -reflux

Slep 2 -esterification

Reagent - ethanol and a concentrated H2SO4condition - reflux

1

'l

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johor stpm trial 2011 chemistry paper 2(no bahasa melayu slide) and answer

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