stpm-trial-2012-chemistry-qa-pahang.pdf

7/27/2019 stpm-trial-2012-chemistry-qa-pahang.pdf

http://slidepdf.com/reader/full/stpm-trial-2012-chemistry-qa-pahangpdf 1/31

1

Trial STPM 962/1 [Turn over (Lihat sebelah)

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

CONFIDENTIAL*/ SULIT*

962/1

TRIAL STPM 2012(PEPERIKSAAN PERCUBAAN STPM 2012)

CHEMISTRY (KIMIA)

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 ARE 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 BERBUA'TDEMIKIAN.

Ada lima puiuh soalan d a l a m 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 10 printed pages.

(Kertas soalan ini terdiri daripada 10 halaman bercetak.)

Percubaan Pahang STPM 2012http://edu.joshuatly.com/ http://fb.me/edu.joshuatly



2



Section A

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

1. and are isotopes of selenium. Which of the following properties is common for

both the isotopes?

A. Nuclear charge B. Nucleon number C. Stability D. Relative isotopic mass

2. Methanethiol, CH3SH undergoes combustion according to the equation shown below.

15 cm3 of methanethiol was exploded with 60 cm3 of oxygen. What would be the final volume(cm3)of the gas mixture obtained at room temperature?

A. 15 B. 30 C. 45 D. 60

3. How many different orbitals are there in the 3 s, 3 p and 3d sub-shells respectively?

A. 1, 3, 5 B. 1, 4, 9 C. 2, 6, 10 D. 2, 8, 18

4. Under what conditions would a gas at low pressure behave more ideally?

A. Molecules at low temperature collide elastically.B. Molecules at high temperature collide elastically.C. Molecules at low temperature collide non-elastically.

D. Molecules at high temperature collide non-elastically.

5. Ice is the crystalline form of water. Which of the following statements is not true about ice?

A. Ice does not conduct electricity.

B. Ice has a giant covalent structure.

C. The bond angle of H−O−H in ice is 109.5D. Ice has a lower density than water at 0ºC due to its open structure.

6. Compounds are either ionic or covalent. Which of the following statements is not true aboutionic bonding?

A. Ionic bonding forms solid compounds.B. Ionic bonding involves ions wit stable electronic configurations.

C. Ionic bonding involves electron transfer from s, p and d -orbitals.D. Ionic bonding’s strength is proportional to the ionic size of ions involved.

7. Which of the following statements is true about the Modern Periodic Table?

A. The arrangement of elements is based on the nucleon number.B. There are 5 main blocks of elements.C. There are 8 groups in the Periodic Table.D. There are 7 periods in the Periodic Table.

CH3SH + 3O2 CO2 + SO2 + 2H2O




3



8. The iodine and propanone reaction is catalysed by acids as shown in the equation below.

Which of the following statements about the reaction is correct if the rate equation is given byrate = k [CH3COCH3][H

+]?

A. The rate determining step does not include the hydrogen ion.B. Product yield is independent of [I2].C. The rate of reaction increases if the [I2] increases.D. k remains constant although the [CH3COCH3], [H

+] and [I2] are increased.

9. Which of the following is a correct statement about the effect of a catalyst?

A. It increases the equilibrium constant for the forward reaction.B. It provides an alternative route for the reaction.C. It increases the rate constant for the forward reaction only.

D. It increases the speed of the reactant particles.

10. The table below shows the values of the ionic product of water, K w at two temperatures.

Temperature/ºC K w / mol dm-

2562

1.00 x 10-14

1.00 x 10

-13

Which of the following statements is true about pure water?

A. At 62 ºC, pH < 7B. At 62 ºC, pH < pOHC. At 62 ºC, pH = 14 − pOHD. The ionic dissociation of water is an exothermic process.

11. A sealed flask with a capacity of 2.0 dm3

contains 0.50 mol of SO2, 0.010 mol of O2 and 4.6mol of SO3 at equilibrium. Calculate K c ( dm3mol-1 ) for the following equilibrium at TºC.

A. 5.9 x 10-5

B. 9.2 x 102

C. 8.5 x 103

D. 1.7 x 104

12. Buffer solutions are an important component of biological systems. Calculate the pH of a buffer solution formed by mixing 100 cm3 of 0.050 mol dm-3 ethanoic acid and 50 cm3 of 0.20 mol dm-3 of sodium ethanoate.

[ K a of ethanoic acid is 1.7 x 10-5

mol dm-3

]

A. 4.1 B. 4.5 C. 5.1 D. 5.4

13. A current of 8A is passed for 100 minutes through molten aluminium oxide using inertelectrodes. What will be the approximate volume of gas liberated, measured at stp?

[ The Faraday constant is 9.65 x 105

Cmol-1

, 1 mole of gas occupies 22.4 dm3

at stp ]

A. 2.8 dm

3

B. 5.6 dm

3

C. 8.4 dm

3

D. 11.2 dm

3

CH3COCH3 + I2 CH2ICOCH3 + HI

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




4



14. What is the standard enthalpy change of formation of hydrogen chloride (kJ mol-1) that can bededuced from the following enthalpy changes shown below?

∆ H ө/kJ mol

-1

N2(g) + 3H2(g) 2NH3(g) − 92

N2(g) + 4H2(g) + Cl2(g) 2NH4Cl (s) − 629

NH3(g) + HCl(g) NH4 Cl(s) −176

A. − 46.3 B. − 92.5 C. − 180 D. − 361

15. In industry, limestone is used to make slaked lime. This preparation involves two stages.

Stage 1: Limestone decomposes at 1000ºC as follows:

CaCO3(s) CaO(s) + CO2(g) ∆ H 1

Stage 2: Calcium oxide is then treated with water:

CaCO3(s) CaO(s) + CO2(g) ∆ H 1

What are the enthalpy changes of these reactions?

∆ H 1 ∆ H 2 A. − −B. − +

C. + −D. + +

16. Which statement about the following equilibrium given below is correct?

A. It is a redox reaction.B. The solution remains yellow throughout the experiment.C. A decrease in pH will result in the increase intensity of orange coloured solution.D. The addition of a suitable catalyst will shift the equilibrium to the left.

17. Which of the following species has the most number of unpaired electrons?

A. 2− B. C. + D.

18. The vapour pressure of pure liquids P and Q at 30 are 48 kPa and 36 kPa respectively. The

total vapour pressure of a liquid mixture of P and Q containing 0.70 mole fraction of Q at 30 is39.6 kPa.

Which of the following statements is true of the liquid mixture?

A. The vapour pressure of Q in the mixture at 30 is 10.8 kPa.

B. Fractional distillation of the mixture yields Q as the distillate.C. The mixture shows a negative deviation from Raoult’s law.

D. P and Q have almost the same strength intermolecular forces.

2CrO42−

(aq) + 2H+

(aq) Cr 2O72−

(aq) + H2O(l)




5



Cu and Zn alloy Carbon

H2SO4 1M

19. The circuit for an electrolysis experiment was set up as shown below.

What are the reactions at the electrodes?

Anode Cathode A. Cu dissolves Cu depositedB. Cu dissolves H2 releasedC. Cu and Zn dissolve Cu depositedD. Zn dissolves H2 released

20. Iron is used as a catalysed in the Haber process to prepare ammonia because the iron

A. has empty d -orbitals.B. has a low activation energy.

C. has many valence electrons.D. can change its oxidation state

21. Which of the following is a the strongest reducing agent?

A. Ba B. Ba2+

C. Mg D. Mg2+

22. An experiment was carried out to investigate the action of concentrated sulphuric acid and phosphoric acid on sodium halides and the observations recorded as follows.

Concentrated acid NaCl NaI

Sulphuric acid white fumes purple vapour

Phosphoric acid white fumes white fumes

Which of the following statements can be deduced from the observations?

A. Concentrated phosphoric acid is a stronger oxidising agent than sulphuric acid.B. Concentrated phosphoric acid is a weaker acid than sulphuric acid.

C. The reducing power of HI is stronger than HCl.D. The bond energy of HI is greater than HCl.

23. A soluble salt sample contains two cations, one of which is Fe2+

. The identity of the secondcation was determined by heating the solid salt with solid NaOH and a colourless gas was released.The gas forms dense white fumes on contact with HCl gas. The residue is grey-green and is insolublein water.

The identities of the gas and residue are probably

Gas Residue A. H2 FeSO4 B. CO2 Fe(OH)3

C. NH3 Fe(OH)2 D. SO2 Fe2(SO4)3




6



24. Which of the following elements has an oxide with a giant structure and a chloride that isreadily hydrolysed?

A. Barium B. carbon C. phosphorus D. silicon

25. The data below refers to calcium as an s-block element and copper as a d -block element.Which of the following property is matched correctly?

Property Ca Cu

A. Density 1.54 8.92B. Melting point 1083 810C. Atomic radius 0.117 0.197D. Electrical conductivity 85 9.6

26. In black and white photographic film, light converts silver chloride into metallic silver. After the film has been developed, the unexposed silver chloride is removed by reaction with sodiumthiosulphate to produce a negative.

Which of the following statements is not true about the reaction?

A. S2O32− ion acts as a ligand.

B. A complex ion is produced.C. [Ag(S2O3)2]

3−ion is linear.

D. Ag undergoes a change in oxidation state.

27. P, Q, R, S are elements of Period 3 in the Periodic Table. The properties of their oxides are as follows.

( i ) Oxide of P is not soluble in both acid and water but dissolves in concentrated NaOH.

( ii ) Oxide of Q is soluble in both aqueous acid and alkali.

( iii ) Oxide of R is soluble in aqueous NaOH.

( iv ) Oxide of S dissolves readily in water to produce an alkaline solution.

Arrange P, Q, R and S in ascending proton number.

A. P, Q, R, S B. S, P, Q, R C. S, Q, P, R D. S, R, P, Q

28. Which of the following statements is true about the chlorides MgCl2, SiCl4 and PCl3?

A. All are liquids at room temperature.

B. MgCl2 is the only chloride with a giant structure.

C. All the chlorides are hydrolysed completely in water.

D. The oxidation states of chlorine in the chlorides are −2, −4 and −3 respectively.

29. Which of the following best explains the role of I−

as a nucleophile?

A. It is a halide.

B. It is negatively charged.

C. It has lone pair electrons.

D. I is a electronegative atom.

30. Which sequence shows the compounds in the order of increasing acidity?

A. CH3COOH, CF3COOH, C2H5OH, C6H5OH C. CF3COOH, CH3COOH, C6H5OH, C2H5OH

B. C2H5OH, C6H5OH, CH3COOH, CF3COOH C. C6H5OH, C2H5OH, CH3COOH CF3COOH,

AgCl + 2S2O32− Cl− + [Ag(S2O3)2]

3−




7



O||

─ C ─CH3CH3COClAlCl3

ClSO3H

ICH3 NH3 CH3

II

SOCl2 SO2 NH2

CH3 O

C H

C

O H

31. Benzene undergoes Friedel-Crafts acylation with ethanoyl chloride to form phenyl ethanoate as shown in

the following reaction.

Which of the following statements is not true about the mechanism.

A. AlCl3 acts as a Lewis acid.B. The overall order of reaction is 1.C. The mechanism involves an electrophile.D. It occurs at room temperature.

32. Saccharine can be manufactured from methylbenzene by a two step reaction as shown below.

─ CH3

Steps I and II follows the following mechanism shown below.

I II

A. Nucleophilic substitution electrophilic substitution

B. Nucleophilic substitution nucleophilic additionC. Electrophilic substitution electrophilic addition

D. Electrophilic substitution nucleophilic substitution

33. What are the expected observation obtained if the following compound

is warmed separately for 10 minutes with Fehling’s and Tollens’ reagents?

Fehling’s reagent Tollen’s reagentA. Brick-red precipitate silver mirror B. No precipitate silver mirror C. Brick-red precipitate no silver mirror D. No precipitate no silver mirror

34. Oxidation of an alkene, R produces a diol. On further oxidation, a diketone is formed.R is probably

A. (C6H5)2C = CH2 B. (CH3)2C = C(CH3)2 C. C6H5CH = CHC6H5 D. CH3CH = C(CH3)2

35. Which reagent produces a colourless mixture when added to phenol?

A. Br 2(aq) B. NaOH(aq) C. FeCl3(aq) D. Universal indicator

36. Which reagent does not react with propanamine?

A. HNO2 B. NaOH C. CH3COCl D. CH3CH2Cl




8



37. When separate samples of R and S are respectively heated with concentrated ammonia and thenreacted with LiAlH4 in dry ether, the same product is formed.

R and S are probably

R SA. C6H5Br C6H5CNB. CH3CH(Br)CH3 CH3CH(CN)CH3 C. CH3CH(Br)CH3 CH3CH2CND. CH3CH2CH2Br CH3CH2CN

38. The repeating unit of a polymer is shown below.

Which of the following statements is not true of the polymer?

A. It can be vulcanised.B. It is elastic.C. It is stable to heat.D. One of its monomers is CHCl = C(CH3)CH = CHCl.

39. An ester W was refluxed with NaOH(aq) and the mixture distilled. The residue gave a whitesolid on acidification and the distillate gives a positive triiodomethane test.

Which of the following substance is W?

A. CH3COOC6H5

B. C6H5COOCH3 C. C6H5COOCH2CH3

D. C6H5COOCH2CH2CH3

40. 2-aminoethanoic acid is not optically active. Which of the following compounds is formed not because of the acid-base property of 2-aminoethanoic acid?

A. H2 NCH2COONaB. CH2OOCCH2 NH2 C. HOOCCH2 NH3ClD. HOOCCH2 NH3OOCCH3

H Cl H CH3 H H| | | | | |

─ C ── C ─ C ── C ═ C ─ C ─

| | |H Cl Cl




9



Section B

For each of the questions in this section, one or more of the three numbered statements 1 to 3 may becorrect. The responses A to D should be selected based on the following.

A B C D

1 onlyis correct

1 and 2 onlyare correct


1, 2 and 3

are correct

41. Gas particle S has a proton number of n and a charge of +1. Gas particle T has a proton number of ( n + 1 ) and is isoelectronic with S. Which of the following statement(s) is/are true about S and T?

1 S has a larger atomic size than T.2 The ionisation energy of S is larger than T.

3 S releases more energy than Y when an electron is added to each particle.

42. A gas behave ideally and is described by the gas equation pV = nRT. Which of the followingstatements is(are) correct about the gas?

1 One mole of any ideal gas occupies the same volume under the same temperature and pressure.

2 The density of an ideal gas at constant pressure is inversely proportional to the temperature.3 Intermolecular forces exists between particles of the gas.

43. Which of the following process have occurred in the following reaction?

1 Neutralisation

2 Formation of ionic bond3 Formation of coordinate bond

44. A mixture of two oxides of Period 3 elements is added to water. The solution formed is almostneutral. The oxides may be

1 Na2O and P4O10 2 MgO and SiO2 3 P4O10 and SO3

45. The charge density of Be2+

ion is similar to Al3+

ion. Which of the following statements is/are

true?1 BeO is basic2 BeCl2 is covalent.

3 Be(NO3)2 (aq) is acidic.

46. Which of the following properties decreases gradually from HCl to HBr to HI?

1 Thermal stability2 Polarity of the H─X bond

3 Boiling point

47. Which of the following reactions occur(s) in a catalytic converter?

1 2CO(g) + O2(g) 2CO(g)

2 2NO(g) + 2CO(g) N2(g) + 2CO2(g)3 2C8H18(g) + 25O2(g) 16CO2(g) + 18H2O(g)

SO3 + H2O + 2NH3 (NH4)2SO4




10



COOH|

HO CH2C−H

|HO NH2

C2H5 C2H5

C = C

H H

A B C D

1 onlyis correct



1, 2 and 3

are correct

48. The structure of dopamine is shown below.

Which of the following statements is(are) correct about dopamine?

1 1 mole of dopamine reacts with 1 mole of HCl(aq).

2 1 mole of dopamine reacts with 3 moles of Br 2(aq).3 1 mole of dopamine reacts with 3 moles of Na2CO3(aq).

49. Which of the following statements is(are) true about the amino acid serine with the structureshown below?

1 Nitrogen gas is released when HNO2 solution is added to serine.

2 NH3 gas is released when serine reacts with NaOH solution.3 The repeating unit of the polypeptide of serine has the structure shown below.

50. Which of the following compound(s) does not have geometrical isomers?

1 2 3

H

|

H2 N − C − COOH

|

CH2OH

H O| ||

───OCH2 − C − C───

|

NH2 n

CH3 C2H5

C = C

H C2H5

H C2H5

C = C

C2H5 CH3




1

Identity card number ................................................ Centre number/index number: ...........................

(Nombor kad pengenalan) (Nombor pusat/angka giliran)

962/2

TRIAL STPM 2012(PEPERIKSAAN PERCUBAAN 2012)

CHEMISTRY (KIMIA)

PAPER 2 (KERTAS 2)

Two and a half hours (Dua jam setengah)

For examiner’s use

1

2

3

4

5

6

7

8

9

10

Total

This question paper consists of 11 printed pages.

Instructions to candidates:

DO NOT OPEN THIS QUESTION PAPER UNTIL

YOU ARE TOLD TO DO SO.

Answer all questions in section A.Write your answers in thespaces provided.All working should be shown.For numerical

answers,units should be quoted wherever they are appropriate.

Answer any four questions in section B.Write your answerson the answer sheets provided.Begin each answer on a freshsheet of paper and arrange your answers in numerical order.Tie

your answer sheets to this question paper.




2

Section A Answer all question in this section.

1. (a) The rate equation for a reaction between substances C and D is:

rate = k [C]2

[D]2

The initial rate is found to be 7.5 × 10 –3 mol dm –3 s –1 when the initial

concentration of C is of 0.25 mol dm –3

and the initial concentration of D is 0.50

mol dm –3.

(i) Calculate the value of the rate constant, k , at this temperature and deduce its

units.

Calculation

Units

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

(ii) On the axes below sketch a graph to show how the value of k varies astemperature is increased over a considerable range.

(4 marks)

Rateconstant

k

Temperature




3

(b) The table give data on some solubilities and solubility products. Some of the data

entries are missing.[C=12, O=16, Cl=35.5, Ca=40, Ag=108]

(i)

Fill in the missing data in the table:

Compound Ksp, mol dm- Solubility, mol dm- Solubility, g dm-

AgI 8.30 x 10-17 9.11 x 10-9 2.14 x 10-6

AgCl 1.8 x 10-10

CaCO3 0.03

[4 marks]

(ii)

Fill in the table below, state and explain what will happen to the solubility products of the silver chloride if the salts mentioned are dissolved in a

saturated solution of silver chloride.(Give the effect on the solubility as

increase, decrease or no change).

Salt Sodium nitrate Sodium chloride

Effect

Explanation

[2 marks]




4

2. Use the data below, where appropriate, to answer the questions which follow.

Standard electrode potentials E /V

2H+(aq) + 2e – H2(g) 0.00

Br 2(aq) + 2e –

2Br –

(aq) +1.09

(aq) + 12H+(aq) + 10e – Br 2(aq) + 6H2O(l) +1.52

Each of the above can be reversed under suitable conditions.

(a) State the hydrogen ion concentration and the hydrogen gas pressure when, at 298K, the potential of the hydrogen electrode is 0.00 V.

Hydrogen ion concentration ......................................................................................

Hydrogen gas pressure ..............................................................................................

[2 marks]

(b) The electrode potential of a hydrogen electrode changes when the hydrogen ionconcentration is reduced. Explain, using Le Chatelier’s principle, why this change

occurs and state how the electrode potential of the hydrogen electrode changes.

Explanation of change

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

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

Change in electrode potential

....................................................................................(3)

– 32BrO




5

(c) A diagram of a cell using platinum electrodes X and Y is shown below.

(i) Use the data above to calculate the e.m.f. of the above cell under standardconditions.

(ii) Write a half-equation for the reaction occurring at electrode X and anoverall equation for the cell reaction which occurs when electrodes X and Y

are connected.

Half-equation

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

Overall equation

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

(iii) Write down the cell diagram to represent the overall reaction in the cell.

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

[5 marks](Total 10 marks)

V

Salt BridgeX Y

Solution containingBr (aq) and Br (aq)

Solution containing BrO (aq),H (aq) and Br (aq) –

–

+2 2

3




6

3. (a) The tetr achlorides of Gr oup 14 elements, example CCl4 , SiCl4 , GeCl4 , SnCl4 and

PbCl4 are liquids at r oom temperatur e. All the tetrachlorides, with the exception of

CCl4, are hydrolysed in aqueous solution to form acidic solutions.

(i) State the molecular shape of all the Gr oup 14 tetrachlor ides.

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

(ii) Write a balanced equation f or the hydrolysis of SiCl4.

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

(iii) Explain why CCl4 docs not under go hydr olysis.

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

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

..........................................................................................................................................[4 marks]

(b) Aqueous aluminium sul phate contains [Al(H2O)6]3+

Aqueous ammonia is added toaqueous aluminium sul phate until in excess. The r eaction that occur s in limited aqueousammonia is as follows.

[Al(H2O)6]3+ (aq) + 3 OH- (aq) Al(H2O)3(OH)3 (s) + 3 H2O (l)

(i) Descri be one o bservation in the above reaction.

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

(ii) What chemical nature of the aluminium ion is shown in (b) (i)?

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

(iii) What happens when excess aqueous ammonia is added to the solution? Write anequation f or the reaction involved.

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

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

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

(iv) What chemical nature of the aluminium ion is shown in (b) (iii) ?

.......................................................................................................................................[6 marks]




7

4. (a) Ethylamine C2H5 NH2 is a f oul smelling liquid that r eacts with dilute hydr ochloric

acid at r oom temperature.

(i) Write a balanced equation f or the reaction between ethylamine and dilutehydrochloric acid.

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

(ii) Name the type of r eaction taking place between ethylamine and dilute

hydr ochloric acid.

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

(iii) State two observable changes for the reaction between ethylamine and dilute

hydrochloric acid.

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

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

[4 marks]

(b) State the reagents and wr ite balanced equations for the pr eparation of ethylamine

from the following compounds.

(i) CH3CH2Br

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

(ii) CH3CN

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

[4 marks]

(c) As pirin has the following structure.

Give the pr oducts formed when as pirin is heated with aqueous potassium hydr oxide

solution.




8

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

[2 marks]

Section B Answer any four (4) questions in this section.

5. (a) Draw sketch graphs of

a. P against V

b. P against 1/V

c. PV againsr P

d. PV against V

for a constant number of moles of an ideal gas at a constant temperature.

[4 marks]

(b)

Plot on separate sketch graphs,(i) V against T (°C)

(ii) V against T (K)

for a constant number of moles of an ideal gas at constant pressure. [2 marks]

(c) 0.50 g of volatile liquid was introduced into a globe of 1000 cm3 capacity. The

globe was heated to 91°C so that all the liquid vaporized. Under these conditions

the vapour pressure exerted a pressure of 0.25 atm. What is the relative molecular

mass of the liquid ? [R =8.31 or 0.0821] [3 marks]

(d) A balloon can hold 1000 cm3

of air before bursting. The balloon contains 975 cm3

of air at 5°C. Will it burst if it is taken into a house at 29°C ? Assume the pressure of

the gas in the balloon remain constant. [3 marks]

(e) Knowing that the density of ice is less than that of water , explain why the slope

of the solid-liquid equilibrium line in the phase diagram of water is in accord with Le

Chatelier Principle. [3 marks]




9

6. Interpret each of the following observations as fully as you can.

(a) The first ionisaion energy of nitrogen is higher than that of either of the

elements immediately preceding or following it in the Periodic Table. [3 marks]

(b) The boiling point of ammonia, NH3(-33°C) is higher than that of phosphine,

PH3(-87°C) [3 marks]

(c) The bond energy of the nitrogen-nitrogen bond in the nitrogen molecule is 944 kJ

mol-1 whereas the bond energy of the carbon-oxygen in carbon monoxide molecule which

is isoelectronic with nitrogen is 1074 kJ mol-1. [3 marks]

(d) the equilibrium constant Kc, for the reaction

N2(g) + 3H2(g) < = > 2NH3(g)

decreases as the temperature rises whereas Kc for the reaction N2(g) + O2(g) < = > 2NO(g)

increases as the temperature rises. [2 marks]

(e) A solution containing NH3(aq) and NH4Cl(aq) acts as buffer solution, resisting

changes in pH when acids or alkalis are added.

Explain the help of equations how this mixture acts as a buffer. [4 marks]

7 (a) The oxides of the Period 3 elements include the following:Al3O3 ; SiO2 ; P4O6.

(i) The melting points of Al3O3, SiO2 and P4O6 are 2040ºC, 1610ºC and

24ºC respectively. Explain the differences in their melting points in terms

of structure and bonding. [6 marks]

(ii) Describe the solubilities of the oxides in water and write balanced

equations for the reaction of the oxides (if any) with water. [4 marks]

(b) [CrCl2(C2O4)2]3- is a complex ion.

(i) Draw all the structural formulae of the isomers of this complex ion

[3 marks]

(ii) State the types of isomerism exhibited by the isomers [2 marks]




10

8 (a) Platinum (II) forms square planar complexes such as [Pt(NH3)2Cl2 ] where as

platinum (IV) forms octahedral complexes such as [Pt (NH3)4CIBr]2+.

(i) Ex plain what is meant by '"'complex Ion'"'. [2 marks]

(ii) Give the IUPAC name for [Pt(NH3)2Cl2 ] and [Pt (NH3)4CIBr]2+. [2 marks]

(iii) Both these complexes exhibit geometrical isomerism. Draw the trans·

isomer for both of them. [2 marks]

(b) A neutral compound H, has the empirical formula, Co(Cl)x (NH3)y. The

percentage by mass of cobalt, nitrogen and hydrogen in the complex is as

follows: Co, 23.52%; N, 28.00%; CI, 42.53%.

When an aqueous solution containing 12.52 g H is reacted with excess AgNO3

solution, 14.35 g of silver chloride is preci pitated. Deduce the structural

formula of the complex. Explain if you expect H to be coloured. [9 marks]

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-chloropropaneis 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.

(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]




11

10. (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.

(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]




12Percubaan Pahang STPM 2012http://edu.joshuatly.com/ http://fb.me/edu.joshuatly



Trial STPM 2012

Chemistry Paper 1

962/1Answers

No. Answer No. Answer 1

2

3

4

5

6

7

8

9

10

11

1213

14

15

16

17

18

19

20

21

22

23

24

25

A

C

A

B

B

D

D

D

B

A

D

CA

B

C

C

B

D

D

A

A

C

C

D

A

26

27

28

29

30

31

32

33

34

35

36

3738

39

40

41

42

43

44

45

46

47

48

49

50

D

C

B

C

B

B

D

B

C

B

B

DC

C

B

A

B

D

A

C

B

D

B

A

A




1

Pahang STPM trial Mark schemeSection A

1. (a)(i) Order with respect to A 1 [1]

Order with respect to B 1 [1]

(c) (i) Calculation k= (1) = 0.48 [1]

Units = mol –3

dm9

s –1

[1]

(ii)

(

(b) (i)

Compound Ksp, mol dm- Solubility, mol dm- Solubility, g dm-

AgI 8.30 x 10-17 9.11 x 10-9 2.14 x 10-6

AgCl 1.8 x 10-10 1.34 x 10-5

1.93 x 10-3

CaCO3 9 x 10-8

3.00 x 10-4

0.03

[4]

(ii)

Salt Sodium nitrate Sodium chloride

Effect No effect Decrease

explanation No common ion Common ion effect

22

3 –

)50.0()25.0(

105.7

23 – 23 –

–1 –3

)dm(mol)dm(mol

sdmmol

(1)

Rate

constant,k

Temperature




2

2. (a) Hydrogen ion concentration: 1.00 mol dm –3 (1)

Hydrogen gas pressure: 100 kPa or 1.0 atm (1)

(b) Explanation of change: Equilibrium displaced to left (1)

to reduce constraint (1)

Change in electrode potential : Becomes negative or decreases (1)

allow more negative

(c) (i) 0.43V (1)

(ii) Half-equation: 2Br – ↔ Br 2 + 2e – (1)

Overall equation: 2BrO3 – + 10Br – + 12H+ -> 6Br 2 + 6H2O (2)

or BrO3 – + 5Br – + 6H+ 3Br 2 + 3H2O

species (1) and balanced (1)

(iii) Pt | Br – , Br 2 || BrO3 – , Br 2, H

+ | Pt

[10]

3 (a) (i) Tetrahedr al .... 1

(ii) SiCl4 + 2 H2O -----> SiO2 + 4 HCl .....1

(iii) has the electronic configuration of 1s22s22p2 . .....1

does not have empty d orbitals, cannot ex pand its valence shell. .....1

OR cannot f onn the intermediate coordinate bond with the water molecule

[4]

(b) (i) A white pr ec i pitate is formed . .....1

(ii) Acidic in natur e . .....1

(iii) The white pr ecipitate is soluble in excess aqueous ammonia . .....1

and f orm a colourless solut ion .....1

Al(H2O)3(OH)3 + OH- → [Al(H2O)2(OH)4]- + H2O .....1

(iv) Acidic in natur e . .....1

. [6] .

. 10 .

4 (a) (i) C2H5 NH2 + HCl → C2H5 NH3+Cl- ......1

(ii) Neutralisation ......1

(iii) The fishy smell of ethylamine disappears ......1

Temperature of mixture rises .....1

(b) (i)

..1+1

(ii)




3

..1+1

(c)

..1+1

4. (a) (i) P (ii) p

V 1/V

(iii) P (iv) PV

P V

[4]

(b) (i) V (ii) V

T, °c T, K

[2]

(b) PV = nRT, PV = (m/M)RT

0.25 X 1 = (0.5/M) x 0.082 x 364

= 60

(d) V1 V2 V1 975

---- = ---- => ----------- = -----------T1 T2 273 + 29 273 + 5

10




4

V1 = > 1000

The balloon will burst.

(e) H2O(l) < ===== > H2O(g)

As pressure increases at constant temperature, this equilibrium shifts to the

liquid phase --- the more dense phase. Thus a movement straight up on the phase

diagram, increasing the pressure at constant temperature causes melting as one

crossees the solid liquid equilibrium line.

Question 6

(a) Ionisation energy o nitrogen is expected to be higher than the elements preceding it

because across the period, affective charge increase (nuclear charge increases, atomic

size decreases) with similar screening effect. [1]The element following nitrogen has the following electronic configuration :

↑↓ ↑↓ ↑↓ ↑ ↑

1s 2s 2p

[1]

The electrons in the 2p-orbital experience electronic repulsion and this makes its

removal easier. Hence, it has a lower ionization energy than nitrogen, [1]

(b) Although phosphine has a larger molecular size than ammonia and hence stronger van

der Waals forces, [1]

it is not capable of intermolecular hydrogen bonding. [1]

On the other hand, due to the high electronegativity of nitrogen and is small size, the

N-H is greatly polarized and hydrogen bonds exist between the ammonia molecules.

More energy required to break the intermolecular hydrogen bond and hence ammonia

has a higher boiling point. [1]

(c) The bond energies of the 2 isoelectronic systems are very endothermic and are similar

to one another. This is due to the strong tripple bonds between the atoms (N≡N and

C≡O). [1]

However, the bond in carbon monoxide is slightly more polar (oxygen is more

electronegative than carbon) and this makes the bond even stronger. Hence, its bondenergy is more endothermic than that of nitrogen. [2]

(d) The synthesis of ammonia is exothermic. Therefore, increasing temperature sifts the

equilibrium position to theleft. Hence, Kc decrease. [1]

However, the formation of nitrogen monoxide is endothermic, increasing temperature

shifts the equilibrium position to the right, Kc increase. [1]

(e) On addition of a small amount of acid, NH3 reacts with the H+ added so that [H+]

remains approximately constant and pH is maintained. [1]

NH3 + H+

---- > NH4+

[1]




5

On addition of a small amount of base, NH4+ reacts with the OH- added so that [OH-]

remains approximately constant and pH is maintained. [1]

NH4+ + OH- ----- > NH3 + H2O [1]

The large reservoir of NH3 and NH4+ in the buffer sufficientlycopes with the addition

of the acid and the base.

Total : 15 marks

7 (a) (i)

Al2O3 SiO2 P4O6

Structure Giant ionic Giant covalent Simple molecule

Bonding Ionic Covalent Weak van der

Waals betweenmolecules

.....1x6

(ii) Al2O3 insoluble in water .........1

SiO2 insoluble in water .........1

P4O6 dissolves in water to form acidic solution .........1

P4O6 + 6H2O → 4 H3PO3 .........1

(b) (i)

Cis isomer [arrow heads not required]

Trans isomer Enantiomer of trans isomer ...1x3




6

(ii) Geometric isomerism

Optical isomerism ... 1x2

15




7

9 (a) (i)

...1x2

Bimolecular nucleophilic substitution .......1

(ii) rate increases ........1

atomic size of bromine > chlorine

C-Br bond is weaker and easier to break .......1

(iii)

..1x4

(b) (i)

..1x2

(ii) serylalanine or alanylserine ......1

(iii)




.......1

10. (a) CH3-CH=CH-CH3 ....1x2

(b) (i) A: CH3CH2Cl B : CH3CH2OH

C : CH2=CH2 D : CH2Br- CH2Br

E : CH2OH – CH2OH ....1x5

(ii) ethanolic KOH ........1

(iii) monomer for polyester ........1

(c) [Suggested answers]

(i) - heat with ethanolic silver nitrate

1-iodohexane : yellow precipitate of AgI

1- chlorohexane : white precipitate of AgCl .......1+1

(ii) - heat with ethanolic silver nitrateChlorocyclohexane : white precipitateChlorobenzene : no precipitate .......1+1

(iii) - add acidified KMnO4

1- chloro-1- butane : decolourisation of KMnO4

1- chlorobutane : KMnO4 solution is not decolourised. ........1+1

15

15

stpm-trial-2012-chemistry-qa-pahang.pdf

Documents