stpm chem 962-1 trials smkbu 2012

8/11/2019 Stpm Chem 962-1 Trials Smkbu 2012

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STPM TRIALS 962/1 1 [Turn over (Lihat sebelah)2012/2013 CONFIDENTIAL*

SULIT*

962/1 STPM TRIALS

CHEMISTRY (KIMIA)

PAPER 1 (KERTAS 1)

One and a half hours (Satu jam setengah)

S.M.K BANDAR UTAMAPETALING JAYA, SELANGOR DARUL EHSAN

PERCUBAAN SIJIL TINGGI PERSEKOLAHAN MALAYSIA(MALAYSIA HIGHER SCHOOL CERTIFICATE TRIALS)

Instructions to candidates:

DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE TOLD TO DO SO.

Answer all questions in Section A. Marks will not be deducted for wrong answers. For each

question, four suggested answers are given. Choose the correct answer and circle the answer.

Answer all questions in Section B. Write your answers in the spaces provided.

Answer any two questions in Section C. All essential working should be shown. Fornumerical answers, unit should be quoted wherever appropriate. Begin each answer on a fresh

sheet of paper and arrange your answers in numerical order.

Arahan kepada calon:

JANGAN BUKA KERTAS SOALAN INI SEHINGGA ANDA DIBENARKAN BERBUAT

DEMIKIAN.

Jawab semuasoalan dalam Bahagian A. Markah tidak akan ditolak bagi jawapan yang

salah. Bagi setiap soalan, empat cadangan jawapan diberikan. Pilih jawapan yang betul dan buatbulatan pada jawapan tersebut.

Jawab semuasoalan dalam Bahagian B. Tulis jawapan anda di ruang yang diberikan.

Jawab mana-mana duasoalan dalam Bahagian C. Semua jalan kerja yang sesuai

hendaklah ditunjukkan. Bagi jawapan berangka, unit hendaklah dinyatakan di mana-mana yang

sesuai. Mulakan setiap jawapan pada helaian kertas jawapan yang baharu dan susun jawapan

anda mengikut tertib berangka.

This question paper consists of printed pages.

(Kertas soalan ini terdiri daripada halaman bercetak.)

CONFIDENTIAL*/SULIT*

Name: Class: LOWER 6 Sc

Lau Kah Pew 2012


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Section A [15 marks]

Answer allquestions in this section.

1. Which one of the following pairs of atoms or ions contains the same number of neutrons?

A) 14C and 12C C) 23Na+and 24Mg2+

B) 19F and 20Ne D) 32S and 27Al

2. Magnesium has three isotopes, 24Mg, 25Mg, and 26Mg. The percentage of each in order is78.7%, 10.1%, 11.2%. Calculate the relative atomic mass of Magnesium.

A) 24.0 B) 24.3 C) 25.0 D) 25.7

3.

V1= 9.0 L

P1 = 2.0 atm

V2= 6.0 L

P2 = 8.0 atm

Two joined vessels containing gas Yand gas Zrespectively at s.t.p. is separated by a valve. Ifboth these gasses do not react, calculate the total pressure of the vessels at equilibrium when thevalve is opened.

A) 3.2 atm B) 4.4 atm C) 5.0 atm D) 10.0 atm

4. A mixture of 16.0 g of oxygen gas and 5.0 g hydrogen gas in a closed vessel exerts a pressure Patmosphere. When 24.0 g of a monoatomic gas, X, is added into the vessel under the sametemperature, the pressure of the mixture becomes 3Patmosphere.

What is the relative atomic mass of gas, X? Assume that the gas behaves ideally and do notreact with one another. [Ar: H = 1.0 ; O =16.0]

A) 4.0 g B) 8.0 g C) 12.0 g D) 24.0 g

5. The designationss,p, and d, in Quantum Mechanics indicate...

A) different electron energy levels.B) the maximum number of valence electrons.

C) different electron orbitals within the energy levels.

D) spin, position, and density of the electron cloud.

6. What hybridization is predicted for the nitrogen atom in NO3ion?

A) sp B) sp2 C) sp3 D) sp3d

Y Z


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7. The line spectrum in Figure 1 below shows part of the emission spectrum of the hydrogen atom.

Figure 1

Which of the following is true of the above spectrum?

A) Line Phas higher frequency than Q.

B) Line Qand line Rbelong to different electrons.

C) Line Qis the convergence limit of Lyman series.

D) Line Sis formed from the electronic transition from n= 3 to n= 2.

8. The phase diagram for a pure substance, X, is shown in Figure 2. The atmospheric pressure is101.3 kPa.

Figure 2

Which of the following statements is CORRECT?

A) Xis a solid at s.t.p.

B) Point Qis the critical point for X

C) The melting point of Xincreases as the pressure decreases.

D) The minimum pressure required to liquefy vapour Xis 200 kPa.

9. What is the meaning of equilibrium vapour pressure?

A) the rate of the forward process is exactly balanced by the rate of the reverse process.

B) the temperature at which the vapour pressure of a liquid is equal to the external pressure.

C) the vapour pressure measured when a dynamic equilibrium exist between condensation andevaporation.

D) the vapour pressure measured when a dynamic equilibrium exist between vaporisation andcondensation.

Ultraviolet region

P Q R S


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10.Ammonia molecule is a trigonal pyramidal in shape with a lone pair of electrons. Which of thefollowing DOES NOT involve the lone pair electrons on the nitrogen atom of the ammoniamolecule?

A) solubility of ammonia in water.

B) reaction between ammonia and copper(II) oxide

C) formation of a coordinate compound with BF3.D) Foundation of dark blue solution when excess ammonia is added to Cu2+(aq).

11.The unit cell in a certain lattice consists of a cube formed by an anion at each corner, an anionin the centre, and a cation at the centre of each face. The unit cell contains a net;

A) 2 anions and 2 cations C) 3 anions and 2 cations

B) 2 anions and 3 cations D) 9 anions and 6 cations

12.

Which of the following molecules are held together by van der Waals forces only?A) Ice B) Protein C) Ammonia D) Dry ice

13.The acid catalysed reaction between propanon and iodine is:

The result of an experiment is shown in Figure 3 below:

Figure 3

From this it can be concluded that

A) the acid is not involved in the reaction.

B) it is a second order reaction overall.

C) the rate-determining step involves only iodine.D) the rate of reaction does not depend on the concentration of iodine.

14.The balanced equation for the reaction of bromated ion with bromide in acidic solution is givenby;

BrO3+ 5Br + 6H+ 3Br2+ 3H2O

At a particular instant in time, the value of = 2.0 x10-3mol dm-3s-1. What is the

value of in the same units?

A) 1.2 x10-3 B) 2.0 x10-3 C) 3.3 x10-3 D) 6.0 x10-3


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15.Which of the following graphs represents an endothermic reaction that has an activation energy,Ea, of 100 kJ?

A) C)

B) D)

Section B [15 marks]

Answer allquestions in this section.

16. The following questions are based on the information given in the table below.

ElementProton

Number

First Ionization Energy

(kJ/mol)

W 9 1,680

X 11 494

Y 24 653

a) (i) Write thespdfnotation for all three of the elements stated above at ground state.

W

X

Y

[2 marks]


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(ii) Which of these elements show anomalous electronic configuration? Explain.

[2 marks]

b) Which would you expect to be more metallic, Wor X? Explain.

[2 marks]

c) Suggest and write the empirical formula for an ionic substance that may be formed by anyof the three elements above.

[1 mark]

17. a) Draw the Lewis structures and state the geometry for the SF6molecule and the XeO2F2molecule.

SF6molecule XeO2F2molecule

Lewis structure: Lewis structure:

Geometry: Geometry:

[4 marks]

c) Determine if the molecules stated above are polar.

[2 marks]


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d) SF6is a very stable and inert molecule compared to SCl6, while SI6does not exist. Why isthis so?

[2 marks]

Section C [30 marks]

Answer any two questions in this section.

18. a) Based on Quantum Mechanics, define an orbital. Following this, sketch the 1sand 2porbitals. Compare their shapes and sizes.

[6 marks]

b) The first order rate constant for the decomposition of ethyl iodide by the reaction:

C2H5I(g)C2H4(g) + HI(g)

The rate constant for this reaction at 600 K is 1.60x

10

-5

s

-1

.i) Determine the time needed for 30% of the initial quantity of ethyl iodide to decompose

at 600 K.

ii) If the activation energy,Ea, for this reaction is 209 kJ mol-1, calculate its rate constant at

700 K.[9 marks]

19. a) Both diethyl ether (an anaesthetic) and butan-1-ol (a solvent used in preparation ofvarnishes) has the same molecular formula of C4H10O. But their structural formulas aredifferent, as shown below:

CH3 CH2 CH2 CH2 OH

butan-1-ol

CH3 CH2 O CH2 CH3

diethyl ether

Compare their vapour pressures (at 25C) and solubility in water. Provide explanations foryour answers.

[7 marks]

Adapted from Chemistry, Brady & Senese, Wiley 2003, 8.150, p351; 12.86, p544


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b) Looking at the phase diagram below for sulphur, answer the following questions:

(i) How many triple points are there? Which phases coexist at the triple points?

(ii) What is the stable phase at 1 atm and 100oC?

(iii) Describe the phase changes when sulphur vapour is cooled from 200oC to 100oC at3.65 x10-3kPa pressure.

[8 marks]

19. a) (i) What does rate of reactionmean?

Two reactants, A and B, react in an inert solvent according to the following equation:

A + 2B AB2

In order to determine the order of reaction between reactants Aand B, a series ofexperiments were conducted. Table 1 below shows the results of the experiments.

Experiment

Initial concentration of Initial Rate of

formation ofAB2(mol dm-3min-1)A(mol dm-3) B(mol dm-3)

1 0.10 0.10 0.0010

2 0.10 0.20 0.0040

3 0.10 0.30 0.0090

4 0.20 0.10 0.0010

5 0.30 0.20 19(a)(iii)

Table 1


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(ii) Determine the orders of reaction with respect to reactants A, and B. Following that,write the rate law for the reaction above.

(iii) Predict the initial rate of reaction of the fifth experiment.[7 marks]

b) The allene molecule, H2CCCH2, has two sets of double bonds. The molecular structureof allene is as follows...

C C C

H

H H

H

(i) What are the hybridisation states of the carbon atoms in this molecule?

(ii) Draw diagrams to show the formation ofsigmabonds andpibonds in allene.[5 marks]

c) Explain why the boiling point of aluminium is higher than sodium. [3 marks]

END OF PAPER

Prepared by, Verified by, Verified by,

....

Lau Kah Pew


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STPM CHEM ISTRY TRIALS 2012 MARK SCHEME

Section A [40 marks]

1. The following questions are based on the information given in the table below.

Element Proton Number First Ionization Energy (kJ/mol)

W 9 1,680

X 11 494

Y 24 653

a) (i) Write thespdfnotation for all three of the elements stated above at ground state.

W

X

Y

[3 marks]

(ii) Which of these elements show anomalous electronic configuration? Explain.

[2 marks]

b) Which would you expect to be more metallic, Wor X? Explain.

[2 marks]

c) Suggest and write the empirical formula for an ionic substance that may be formed by any of the three elementsabove.

[2 marks]

e) Yion forms a complex hexa-aqua ion with +3 charge which is green in colour. Draw the Lewis structure for

this complex ion.

[1 mark]

2. Acetylene, C2H2, an important fuel in welding, is produced in the laboratory when calcium carbide, CaC2, reacts withwater.

CaC2 (s) + 2H2O(l) C2H2 (g) + Ca(OH)2

For a sample of acetylene that is collected over water, the total gas pressure is 98.4 kPa and the volume is 500 cm3at

25C.

a) Assuming the acetylene gas collected is pure and that no water vapour is present, determine the number of


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moles of acetylene that is formed from the reaction.

PV = nRT

n = PV/RT = (98.4x103)(0.500x10

-3)/(8.314x298) = 0.0203 mol

[3 marks]

b) The enthalpy of combustion of C2H2is ...

(i) Write a balanced chemical equation for the enthalpy of combustion of acetylene.

[1 mark]

(ii) Based on your answer in 2(a), calculate the amount of heat that would be produced if all the acetyleneproduced in the reaction mentioned above were to be completely combusted in excess oxygen gas.

[2 marks]

c) (i) Draw the Lewis structure for C2H2.

[1 mark]

(ii) State the hybridisation that exists for each carbon atoms in the C2H2molecule.

[1 mark]

(iii) Describe the covalent bond that exists between the two carbon atoms.

[2 marks]

Adapted from Silberberg, Chemistry, 5.9, p194

3. Ethanoic acid, CH3COOH, is formed as vinegar by the bacterial oxidation of ethanol present in wine and othersolutions. Ethanoic acid can also be formed in the laboratory by the oxidation of ethanol.

a) (i) What oxidising agent is used for this laboratory experiment? State the colour change that would beobserved.

[2 marks]

(ii) Write an equation to show the reaction mentioned in 3(a)(i).

[1 mark]

When ethanoic acid is prepared in this way in the laboratory, the reagents are heated under reflux for some time

before the ethanoic acid is separated.

b) (i) Why is the reaction carried out by heating under reflux?


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[1 mark]

(ii) What would be the main organic compound formed if, instead of heating under reflux, the reagents wereleft to react at room temperature?

[1 mark]

Presence of other functional groups in the molecular structure of a carboxylic acid may affect its acidity.

H3C C

O

OH

CH2 C

O

OH

H3C CH2 C

O

OH

Cl

c) (i) Arrange the carboxylic acids above in increasing acidity.

[1 mark]

(ii) Briefly explain your answer in 3(c)(i)

[2 marks]

d) Ethanoic acid can be used to prepare a buffer solution.

(i) State one chemical that needs to be added to CH3COOH to produce a buffer solution.

[1 mark]

(ii) Give the structural formulae of the species that are responsible for the buffer action of the solution.

[1 mark]Adapted from UCLES A-level, Chemistry P2, Oct/Nov 2007, Qs 5

4. a) What does rate of reactionmean?

[1 mark]

b) Two reactants, Aand B, react in an inert solvent according to the following equation:

A + 2B AB2

In order to determine the order of reaction between reactants Aand B, a series of experiments were conducted.The following are the results of the experiments.


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Experiment

Initial concentration of Initial Rate of

formation ofAB2(moldm-3min-1)A(mol dm-3) B(mol dm-3)

1 0.10 0.10 0.0010

2 0.10 0.20 0.0040

3 0.10 0.30 0.0090

4 0.20 0.10 0.0010

5 0.30 0.20 4(b)(iv)

Table 1

b) (i) What are the orders of reaction with respect to reactants A, and B?

[2 marks]

(ii) Write the rate law for the reaction above.

[1 mark]

(iii) Determine the value of the rate constant. State its units.

[2 marks]

(iv) Predict the initial rate for the production of AB2in experiment 5.


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[1 mark]

(v) Suggest a possible reaction mechanism by writing a series of elementary steps for the reaction betweenAand Bthat is consistent with the observations of the experiment data given in Table 1.

[3 marks]

Section B [60 marks]

Answer any fourquestions in this section

5. a) Bhr model of the Hydrogen atom states that its electron moves around the nucleus along fixed paths. Theorbital of the electron, n, depends on its energy level that is described by the equation,

(n= 1, 2, 3, )

WhereEis the energy of the electron and bis the combined constant with a value; 2.18 x10-18J.

The removal of an electron from the hydrogen atom corresponds to raising the electron from ground state tothe Bhr orbit; n= . On the basis of this statement, calculate the ionisation energy of hydrogen in kilojoulesper mole.

[4 marks]

b) Based on Quantum Mechanics, define an orbital. Following this, sketch the 1sand 2porbitals. Compare theirshapes and sizes.

[4 marks]

c) Both diethyl ether (an anaesthetic) and butan-1-ol (a solvent used in preparation of varnishes) has the samemolecular formula of C4H10O. But their structural formulas are different, as shown below:

CH3 CH2 CH2 CH2 OH

butan-1-ol

CH3 CH2 O CH2 CH3

diethyl ether

Compare their vapour pressures (at 25C) and solubility in water. Provide explanations for your answers.[7 marks]

Adapted from Chemistry, Brady & Senese, Wiley 2003, 8.150, p351; 12.86, p544

6. a) A hydrocarbon with an empirical formula of C7H6, and a relative molecular mass of 180 contains 93.33%carbon by mass.

(i) Determine the molecular formula of the hydrocarbon.[5 marks]


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(ii) This hydrocarbon has two structural isomers, Xand Y; that contains two benzene rings respectively. Xexhibits geometrical isomerism, but Ydoes not. In their reactions with HBr, Xforms a bromoalkane,Q, that is optically active; while Yforms Rthat is optically inactive. Determine the structures of X, Y,Qand R. Draw the structure for the enantiomers of Q.

[6 marks]

Adapted from STPM Chemistry, 1999, P2, Qs7a

b) The bond angles in nitrite ion, NO2, and nitronium ion, NO2+, are 115 and 180, respectively. Rationalize

these values using Lewis structures and VSEPR theory.[4 marks]

Adapted from Silberberg, Chemistry, 14.172, p.605

7. a) Explain and describe how each of the following changes, down the Group 2 elements (from beryllium tobarium)

(i) first ionisation energy

(ii) the solubilities of the sulphate salts in water[8 marks]

Adapted from STPM Chemistry, 2000, P2, Qs6a

b) Magnesium hydroxide, Mg(OH)2, is almost insoluble in water. It has a solubility product, Ksp, of 2.0 x10-11.

(i) Write an expression for theKspof magnesium hydroxide. Then using the value given, calculate theconcentration of Mg(OH)2in a saturated solution.

(ii) Explain whether magnesium hydroxide would be more or less soluble in 0.10 mol dm-3of magnesiumsulphate, MgSO4, solution than in water.

[7 marks]

Adapted from UCLES A-level, Chemistry P4, Oct/Nov 2007, Qs 2

8. a) (i) Complete the following reaction scheme which starts with ethanal. Draw and name the structuralformula of the organic compound V, W, X, Yand Z; that would be formed. Suggest also the reactionconditions Qin order to produce the final product; mesoxalic acid.

H3C C

O

H

NaBH4

V

HCN

W

X Ydilute H2SO4

heat

concentrated H2SO4

Tollen's reagent

heatH2C CH C

OH

O

cold dilute MnO4-/H+

Z

Q

C C C

OH

OO

HO

O

[6 marks]

(ii) Suggest a simple test to differentiate organic compounds Vand W. State the observations of your

suggested test.[3 marks]


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b) Carbon monoxide, CO, is used in metallurgy to remove oxygen from metal oxides and thereby give the freemetal. The thermochemical equation for the reaction of CO with iron(III) oxide, Fe2O3, is

Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) H =26.7 kJ

Use this equation and the equation for the combustion of carbon monoxide;

CO(g) + O2(g) CO2(g) H =283.0 kJ

To calculate the value of enthalpy of formation of iron(III) oxide.[6 marks]

Adapted from Chemistry, Brady & Senese, Wiley 2003, 7.11, p286

9. a) The common oxidation states for transition metals ions are +2 and +3. the graph below, shows the trend instandard reduction potential for M3+(aq)/M2+(aq) system for several transition metal ions.

(i) Name an ion that is stable in the +2 oxidation state in aqueous solution. Explain your answer. Takenote that theEO2,H+/H2O

= +1.23.

[4 marks]

(ii) An aqueous solution of iron(II) ions undergoes changes in colour from pale green to yellow whenexposed to air. Explain the observation. Refer to the Data Booklet for more information on theappropriate standard reduction potential values.

[4 marks]

Adapted from STPM Chemistry, 2004, P2, Qs8b

b) Amine bases are notorious for having foul odours. Putrescine, NH2CH2CH2CH2CH2NH2, once thought to befound only in rotting animal tissue, is now known to be a component in all cells and essential for their normaland abnormal (cancerous) growth.

(i) A 0.10 mol dm-3aqueous solution of putrescine is found to have a concentration of 2.1 x10-3mol dm-3of hydroxide ion. What is itsKb?

4.5 x10-5

[4 marks]

Ti V Cr Mn Fe Co

-0.5

0

0.5

1.0

1.5

Standard electrodepotential/V


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(ii) Putrescine can form a polyamide when reacted with a dicarboxylic acid, a molecule with twoCOOHgroup). Suggest a structure of this acid. Describe and write a chemical reaction to show the formationof this polymer.

[3 marks]


10. a) The Group 15 hydrides react with boron trihalides in a reversible Lewis acid-base reaction. When 0.15 mol ofPH3BCl3(s) is introduced into a 3.0 dm

3container at a certain temperature, 8.4 x10-3mol of PH3is present atequilibrium.

PH3BCl3(s) PH3(g) + BCl3(g)

(i) Calculate the equilibrium constant,Kc, for the reaction at this temperature.[4 marks]

(ii) Draw a Lewis structure for the reactant.[2 marks]


b) Complete the following organic reactions. Identify the product and/or the reaction conditions. Write youranswers in structural formulae. If there is more than one product for the reaction, identify the major productand explain how it is determined to be so.

(i)

CH3 C CH2

CH3

[3]majorMarkovnikov's Rule

+ HBr CH3 C CH2

CH3

CH3 C CH2

CH3

Br H H Br

(ii)

KOHCH3 CH2 C CH3

Br

alcohol

CH3

CH3 CH2 C CH2

CH3

CH3 CH C CH3

CH3

major

Sayzeff's rule [3]

(iii) NO2

+ CH3

Cl

NO2

AlCl3

CH3

NO2

CH3

NO2

CH3

major [3]

(iv)

SOCl2OH

O

Cl

O

[1]

[10, max 9 marks]


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a) Spider silk is a natural structural protein, which belongs to the same group as collagen and keratin. It containsa high proportion of the amino acid glycine and alanine.

(i) Give the IUPAC names for glycine and alanine. [2 marks]

(ii) Draw the structures of the tripeptide Gly-Ala-Gly, showing the displayed structure of the peptidelinkages. Describe the type of reaction that takes place during the formation of a peptide.

[4 marks]Adapted from UCLES A-level, Chemistry P6, May/June 2006, Qs 1

stpm chem 962-1 trials smkbu 2012

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