actual 2006 stpm chemistry

1 Majlis Peperiksaan Malaysia 2006

2006 STPM Chemistry Papers 1 and 2

There are fifty questions in this paper. Answer all questions. Marks will not be deducted for wrong answers.

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

Time: 1h 45 min

1. 126C and 14

6C atoms are isotopes of carbon.

Which of the following is the same for the isotopes?A StabilityB Nuclear chargeC Nucleon numberD Relative isotopic mass

2. The values of Ka of several substances are

given in the following table.

Substance Ka/ mol dm3

HCOOH 1.7 104

CH3COOH 1.8 105

OH 1.3 1010

COOH 6.5 105

Which of the following is the strongest base?A HCOO C O

B CH3COO

D COO

3. The boiling points of CH3 OH and CH3SH are 64.5 C and 5.8 C respectively. What is the cause of the difference in the boiling points?A The OH bond is stronger than the SH

bond.B Hydrogen bonds exist between CH3OH

molecules.

C CH3SH molecule is bigger than CH3OH molecule.

D The electronegativity of oxygen is higher than that of sulphur.

4. The table below shows the sizes and charges of six ions.

Ion Radius/nm ChargeU 0.181 +1V 0.135 +2W 0.151 +2X 0.169 1Y 0.182 1Z 0.065 2

Which of the following represents the correct ascending order of lattice energy?A UX < UY < WZ C UY < UX < WZ B UX < WZ < VY D VY < UX < WZ

5. Which of the following is not required in the calculation of the lattice energy of calcium oxide using the Born-Haber cycle?A Enthalpy of hydrationB Enthalpy of ionisationC Enthalpy of atomisationD Electron affinity

6. The kinetic data for the reaction A + 2B C at a certain temperature is shown in the following table.

Section A

Booklet 2006 STPM Chem P1 & 2(08)3rd.indd 1Booklet 2006 STPM Chem P1 & 2(08)3rd.indd 1 2/25/2008 5:39:43 PM2/25/2008 5:39:43 PM



ExperimentInitial

concentration Initial rate of reaction[A]0 [B]0

1 a b r2 2a b 4r3 a 2b r

What is the rate of the reaction?A k[A]2 C k[A][B]2B k[B]2 D k[A]2[B]

7. The reaction in the preparation of sulphur trioxide is shown below.

2SO2(g) + O2(g) 2SO3(g); H = 197 kJ Sulphur dioxide and oxygen are passed over

a heated vanadium(V) oxide catalyst. Which of the following may increase the formation of sulphur trioxide?A Reduction in pressureB Decrease in temperatureC Addition of a promoter to the catalystD Increase in the volume of the container

8. MX, MY and MZ are sparingly soluble salts. When aqueous MNO3 is added dropwise to an aqueous solution containing X , Y and Z ions, MX is precipitated. When aqueous NaZ is added to a small amount of MY precipitate, MY dissolves and MZ is precipitated. The sequence of MX, MY and MZ according to the descending order of their solubility products isA MX, MY, MZ C MY, MZ, MXB MX, MZ, MY D MZ, MY, MX

9. Compounds have either ionic or covalent bonds or both. Which of the following statements is not true of ionic bonds?A They involve the transfer of one or more

electrons from s, p or d orbitals.B The strength of ionic bonds is proportional

to the size of the ions.C They involve ions with stable electronic

configurations.D They result in the formation of solid

compounds.

10. Phosphorus pentachloride decomposes according to the equation

PCl5(g) PCl3(g) + Cl2(g).

When 1.3 102 mol PCl5 is heated at 727 Cin a 1 dm3 flask, the total pressure formed is 150 kPa. What is the partial pressure of chlorine in the flask?

[R = 8.31 J K1 mol1]A 29 kPa C 42 kPaB 32 kPa D 73 kPa

11. Which of the following statements is true of the Periodic Table?A It is built based on the nucleon number.B The elements are divided into five blocks.C There are eight groups in the Periodic

Table.D There are seven periods in the Periodic

Table.

12. The graph below shows the variation of the concentrations of the gases X, Y and Z at T C for the reaction

Which of the following statements is true of the above reaction?A The equilibrium constant K

c can be

calculated at 7 minutes.B The equilibrium constant K

c at 5 minutes

is the same as that at 10 minutes.C The changes of the concentrations of X,

Y and Z at 7 to 10 minutes are due to the increase in the pressure of the system.

D The changes of the concentrations of X, Y and Z at 7 to 10 minutes are due to the increase in the temperature of the system.

13. A 2.0 dm3 stoppered flask at T C contains 0.50 mol of SO2, 0.010 mol of O2 and 4.6 mol of SO3 at equilibrium. Calculate Kc for the following equilibrium at T C.

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

Time/min

X(g) + Y(g) Z(g); H = positive

Concentration/ mol dm3

0 5 7 10

X

Y

Z




A 5.9 105 dm3 mol1B 9.2 102 dm3 mol1C 8.5 103 dm3 mol1D 1.7 104 dm3 mol1

14. Mercury and diaphragm cells are used in industrial processes for the electrolysis of brine. Which of the following is not the product of the two processes?A Sodium metalB Sodium hydroxide solutionC Chlorine gasD Hydrogen gas

15. Buffer solutions are very important to chemical and biological systems. Calculate the pH of a buffer solution formed by mixing 100 cm3 of 0.050 mol dm3 ethanoic acid and 50 cm3 of 0.20 mol dm3 sodium ethanoate.

[Ka for ethanoic acid is 1.7 105 mol dm3.]

A 4.1 C 5.1B 4.5 D 5.4

16. Which of the following species has the most number of unpaired electrons?A 7N

2 C 12Mg+B 8O D 21Sc

17. Which of the following statements is true of Grignard reagents?A They are sources of halogens.B Their Lewis structures are RMg X

:.

C Their reactions involve homolysis of the RMg bond.

D They are formed from reactions between haloalkanes and magnesium metal in anhydrous alcohols.

18. The respective electrolytes of three electrolytic cells are aqueous sodium hydroxide, concentrated aqueous sodium chloride and aqueous silver nitrate. Each cell has carbon electrodes connected in series. What is the ratio of the number of moles of hydrogen gas in the first cell, chlorine gas in the second cell and oxygen gas in the third cell when an electric current flows through the three cells?A 1:1:0 C 1:1:2B 1:1:1 D 2:2:1

19. The vapour pressures of pure liquids X and Y at 25 C are 48 kPa and 36 kPa respectively. The total vapour pressure of a mixture of the two liquids with a 0.30 mole fraction of X at the same temperature is 39.6 kPa.

Which of the following statements is true of the mixture?A The mixture shows a negative deviation

from Raoults law.B Fractional distillation of the mixture

yields Y as the distillate.C The vapour pressure of Y in the mixture

at 25 C is 10.8 kPa.D The strengths of intermolecular forces of

X and Y are about the same.

20. A Ziegler-Natta catalyst is used to produce high density polyethene because the titanium(IV) ion in the catalystA has empty d orbitalB has a low activation energyC has many valence electronsD can change its oxidation states

21. Transition elements have variable oxidation states in complex ions. What are the correct oxidation states of iron in the following complex ions?

[Fe(en)2(SCN)2]+ [Fe(EDTA)]2A +2 +2B +2 +3C +3 +2D +3 +3

22. Astatine is an element in Group 17 of the Periodic Table. What are the expected properties of astatine at 25 C?

Colour Physical state

Oxidising power

A Black Solid WeakB Black Solid StrongC Violet Solid StrongD Violet Liquid Weak

23. Which of the following chlorides fumes in moist air?A PbCl2 C CCl4B SnCl2 D PbCl4




24. The sequence of reactions for an oxide, X, is shown in the scheme below.

Fe2+(aq) X + NaOH(aq) Y(aq) Yellow solution X could be

A MgO C SiO2B Al2O3 D Cl2O7

25. Aqueous sodium chloride, concentrated aqueous ammonia and aqueous potassium iodide are added sequentially to aqueous silver nitrate in a test tube.

Which of the following graphs represents the height of the precipitate formed after the addition of each of the reagents?A C

B D

26. The photochemical smog is a type of air pollution. The gas which causes the pollution isA O3 C NO2B NO D SO2

27. The reactions in the manufacture of nitric acid by the Ostwald process are as follows:

4NH3 + 5O2 4NO + 6H2O 2NO + O2 2NO2 3NO2 + H2O 2HNO3 + NO What is the theoretical percentage yield of

nitric acid obtained from 1 mol of NH3?A 24% C 50%B 31% D 67%

28. When water is added to a compound X, a vigorous reaction occurs which evolves white fumes of hydrogen chloride.

What is the chemical formula of X?A CH3COCl C CH3NH3+ClB CH3CH2Cl D CH2ClCH2OH

29. An hydroxy compound has the following properties. I It is optically active. II It undergoes dehydration to form a

compound without isomer.III It forms a yellow precipitate when heated

with alkaline iodine solution. The compound could be

A CH3CH2OHB CH3CH2CH(OH)CH3C HOCHCH3

D HOCHCH3 | CH2

30. The suitable reagent used to differentiate benzene from 2-hexene isA Cl2 C H2SO4B HBr D KMnO4

31. Which of the following reaction schemes can be used for the preparation of benzoic acid?

A

B

C

D

32. Which of the following best explains the function of OH ion as a nucleophile?A It is alkaline.B It is negatively charged.C It has lone pair electrons.D It has a highly electronegative oxygen

atom.

1. KMnO4, OH

,

2. H3O+

CH3Cl

AlCl3ProductIntermediate

1. KCN

2. H3O+

Cl2Fe Product

Intermediate

Excess H2Ni

CH3COCl


Conc.H2SO4Conc.HNO3

CH3Cl


Height of the precipitate

NaCI NH3 KI NaCI NH3 KI



NaCI NH3 KI NaCI NH3 KI





33. Which of the following compounds can form condensation homopolymers?A CH2 = CHClB CH2 = C(CH3)COOCH3C H2NCH2CH2CH2CH2NH2D H2NCH2CH2CH2CH2COOH

34. The structural formula of a compound is as follows.

CH3C = CHCH2CH2C = CHCHO | | CH3 CH3 What is its IUPAC name?

A 2, 6-Dimethyl-2, 6-octadienalB 2, 6-Dimethyl-3, 7-octadienalC 3, 7-Dimethyl-2, 6-octadienalD 3, 7-Dimethyl-3, 7-octadienal

35. Which of the following could not be used to differentiate between CH3CHO and CH3COCH3?A Tollens reagentB Fehlings solutionC Iodoform testD Mass spectrometry

36. A compound X with the molecular formula C8H8Cl2 produces a compound Y after it is refluxed with alcoholic sodium hydroxide. Compound Y which is produced from 1.75 gof compound X can absorb 210 cm3 of hydrogen gas at 25 C and 1.1 105 Pa.

Which of the following is the structural formula of X?

[Relative molecular mass of X is 175; molar gas constant is 8.31 J K1 mol1]A C

B D

37. Hydrocarbons undergo various reactions. One of the reactions involving 3, 3-dimethyloctane is shown below.

3, 3-Dimethyloctane X Products X could be

A 450 C, Al2O3/SiO2B H2SO4(conc.), 180 CC NaOH(aq), refluxD KCN(aq)/ ethanol, reflux

38. A weak acid X with molecular formula C6H6O reacts with sodium metal and aqueous sodium hydroxide. When a mixture of X and hydrogen gas is passed over platinum,A a tertiary alcohol is formedB substitution reaction occursC the product has the molecular formula

C6H12OD the product is in the same homologous

series as X

39. The repeating unit of a polymer is shown below

Which of the following statements is not true of the polymer?A It is elastic.B It is thermally stable.C It can be vulcanised.D Its monomers are CH=CH2 and

CH2 = C(CH3)CH=CH2.

40. Glycine (2-aminoethanoic acid) is an optically inactive amino acid. Which of the following compounds is formed not because of the acid-base property of glycine?A H2NCH2COONaB CH3OOCCH2NH2C HOOCCH2NH3ClD HOOCCH2NH3OOCCH3

H H | |CCH | | C1

C1

H H | |Cl CCH | | H

Cl

Cl H | |CCH | | Cl

H

H H | |Cl CCH | | H

HC1

H H H CH3 H H | | | | | |CCCCCC | | | | H

H H




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

A B C D1 only is correct.

1 and 2 only are correct.

2 and 3 only are correct.

1, 2 and 3 are correct.

41. The energy-level diagram for a hydrogen atom shows several electronic transitions with frequencies f1, f2, f3, f4 and f5.

Which of the following statements is/are true of the above diagram? 1 f1 represents the convergence limit of the

Lyman series. 2 f1, f2 and f3 represent lines in the Lyman

series. 3 f4 and f5 are used to calculate the difference

between the energy levels of n = 3 and n = 4.

42. The element X has a proton number 25. Which of the following statements is/are true of X? 1 The metal X has a high density. 2 X forms coloured complex ions. 3 The highest oxidation number of X in its

ion is +7.

43. The graph below shows the effect of temperature T on the equilibrium constant, Kp, for the reaction X(g) + Y(g) Z(g).

Which of the following conclusions about the graph is/are correct?

1 The forward reaction is endothermic. 2 At high pressures, the amount of Z in the

equilibrium mixture increases. 3 At high temperatures, the amount of Z in

the equilibrium mixture increases.

44. The Boltzmann distribution curves at temperatures T1 and T2 are shown below.

At temperature T1, 1 the activation energy is lower 2 more molecules have lower energy 3 the total number of molecules remains

constant

45. Silicon is a semiconductor. The electrical conductivity of silicon can be increased by 1 doping with boron 2 doping with phosphorus 3 increasing the temperature

46. The charge density of beryllium ion is similar to that of aluminium ion.

Which of the following statements is/are true? 1 Beryllium oxide is basic. 2 Beryllium chloride is covalent. 3 Aqueous beryllium chloride is acidic.

47. Which of the following reactions occur(s) in a catalytic converter? 1 2CO(g) + O2(g) 2CO2(g) 2 2NO(g) + 2CO(g) N2(g) + 2CO2(g) 3 2C8H18(g) + 25O2(g) 16CO2(g) +

18H2O(g)48. Which of the following compounds is/are the

major product(s) when p-methylphenol reacts with aqueous bromine?1 2 3

Br CH3Br

OH

CH3Br

OHBr

CH3

BrOH

f1 f2 f3

f4 f5

Energy

n = n = 4n = 3

n = 2

n = 1

Kp

1

T

T2T1

EaEnergy

Fraction of molecules

Section B




49. The structural formula of 4-(aminomethyl) aniline is

This compound can be prepared by 1 the reduction of O2N C N by hydrogen with a nickel catalyst 2 the heating of a mixture of concentrated ammonia and Cl CH2Cl 3 the addition of CH3NH2 to H2N Cl

with an iron powder catalyst

50. Most simple esters give the odours of fruits and flowers. Which of the following statements is/are true of the ester

CH=CHCOOCH2CH3? 1 It reacts with LiAlH4 to form

CH2CH2CH2OH and CH3CH2OH. 2 It undergoes saponification to form

CH=CHCOONa+ and CH3CH2OH. 3 It reacts with aqueous bromine to form CHCHCOOCH2CH3.

| | OH Br

H2N CH2NH2.




Time: 2h 30 min

Section A [40 marks]

Answer all questions in this section.

1. (a) X is an element in Period 4 of the Periodic Table. The stable oxides of X are XO, X2O3 and X3O4. An aqueous solution of X

3+ is yellow. X can conduct electricity in the solid and

molten states. (i) What is X?

[1 mark]

(ii) Explain the electrical conductivity of X.

[1 mark]

(iii) Compare the electrical conductivity of X with that of potassium. Explain your answer.

[2 marks]

(b) The following diagram shows the Born-Haber cycle for the formation of X2O3 from its elements under standard conditions.

Answer all questions in Section A. Write your answers in the spaces 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 answers on the answer sheets provided. Begin each answer on a fresh sheet of paper and arrange your answers in numerical order. Tie your answer sheets to this question paper. Answers may be written in either English or Malay.A Data Booklet and graph paper are provided.

2X3+(g) + 3O2(g) H5 = +1950.0 kJ2X3+(g) + 3O(g) H42X(g) + 3O(g)2X(s) + 3O(g) H3 = +831.0 kJ

32X(s) + O2(g) H2 = +742.5 kJ 2

X2O3(s) H1 = 1117.1 kJ

Energy H6 = Lattice energy




(i) Write an equation for the atomisation of oxygen.

[1 mark]

(ii) Calculate the enthalpy change of atomisation for oxygen.

[1 mark] (iii) By referring to the Data Booklet, calculate H4.

[2 marks]

(iv) Compare the lattice energy of X2O3 with that of XO. Explain your answer.

[2 marks]

2. (a) Chemists of ancient times prepared phosphorus, P, from urine. (i) Write the electronic configuration of the phosphorus atom.

[1 mark]

(ii) Draw the shape of one orbital containing the valence electrons of the phosphorus atom.

[1 mark]

(iii) State one of the phosphorus atomic orbitals that are filled according to Hunds rule.

[1 mark]

(iv) In urine, the phosphorus element exists as phosphate ion, PO43. What is the shape of this ion?

[1 mark]

(b) Element X reacts with element Y to form compound Z. The electronegativity values of X and Y atoms are 1.0 and 3.5 respectively. (i) State the type of chemical bond in Z.

[1 mark]




(ii) The Lewis symbols for atoms X and Y are shown below.

What is the chemical formula of Z?

[1 mark] (iii) State two physical properties of Z.

[2 marks]

(iv) The decimal bond in Z is stronger than that in Na2O. State two factors that explain this difference.

[2 marks]

3. (a) The two common oxides of lead are lead(II) oxide and lead(IV) oxide. Lead(II) oxide dissolves readily in aqueous nitric acid. Lead(IV) oxide reacts with concentrated hydrochloric acid to form lead(II) chloride and chlorine. (i) Write a balanced equation for the reaction between lead(II) oxide and aqueous nitric

acid.

[1 mark]

(ii) What is the property shown by lead(II) oxide in the reaction in (i)?

[1 mark]

(iii) Write a balanced equation for the reaction between lead(IV) oxide and concentrated hydrochloric acid.

[1 mark]

(iv) State a change in the oxidation number of lead in the reaction in (iii).

[1 mark]

(v) What is the property shown by lead(IV) oxide in this reaction.

[1 mark]

Atom YAtom X




(vi) State the relative stability of lead(II) and lead(IV) compounds.

[1 mark]

(b) The standard reduction potentials E for several half-cells at 25 C are as follows.

E/V I2(aq) + 2e 2I(aq) +0.54 H2O2(l) + 2H+(aq) + 2e 2H2O(l) +1.77 S4O6

2(aq) + 2e 2S2O32(aq) +0.09

(i) Arrange I2, H2O2 and S4O62 in ascending order of the tendency to be reduced in aqueous solutions.

[1 mark]

(ii) What would be observed if a few drops of acidified aqueous hydrogen peroxide are added to excess aqueous potassium iodide? Explain your answer.

[2 marks]

(iii) What would be observed if tetrachloromethane is added to the products of the reaction mixture in (ii) which is shaken?

[1 mark]

4. (a) The following scheme shows several chemical reactions of 4-nitroaniline.

(i) Write the structural formulae of compounds X, Y and Z in the boxes provided above.

[3 marks]

O2N NH2NaNO2/HCl

0 5 C

OHOH

Z Y

X

HCl (aq)




(ii) Write an equation for the formation of 4-nitroaniline from Z.

[1 mark]

(iii) Why is the formation of 4-nitroaniline from Z possible?

[1 mark](b) Aspartic acid is used in the preparation of aspartame, an artificial sweetener. The structure

of aspartic acid is as follows.

(i) State the IUPAC name of aspartic acid.

[1 mark]

(ii) Draw the structures of the dipeptides formed from aspartic acid.

[2 marks]

(iii) Name the bond between the dipeptide molecules other than hydrogen bond.

[1 mark]

(iv) State one method of separating a mixture of aspartic acid and glycine.

[1 mark]

H OH | |HNCCO | | H CH2 |

CO | OH




Section B [60 marks]

Answer any four questions in this section.

5. (a) An element X is in Group 9 and Period 4 in the Periodic Table. (i) Discuss the application of the Aufbaus principle in the construction of the electronic

configuration of X. [3 marks] (ii) Name one element which has almost the same radius as X. Give three reasons for

your answer. [4 marks](b) Peroxyacetyl nitrate (PAN) is an air pollutant formed in the photochemical smog. The

concentration of PAN in a polluted air sample is analysed at 25 C. The results are given in the table below.

Time/ min 0 10.0 20.0 30.0 40.0 50.0 60.0Concentration of PAN/ 1010 mol dm3 8.4 6.6 5.3 4.2 3.5 2.8 2.1

(i) Determine graphically the order of the decomposition of PAN at 25 C. [4 marks] (ii) Calculate the rate constant for the decomposition of PAN at 25 C. [2 marks] (iii) Predict the concentration of PAN in air at 25 C after 90 minutes. [2 marks]

6. (a) Pure nitric(V) acid is a colourless liquid which forms an azeotropic mixture with water. Aqueous nitric(V) acid shows a negative deviation from Raoults law. (i) Explain why aqueous nitric(V) acid shows a negative deviation. [2 marks] (ii) Sketch a boiling point-composition diagram for aqueous nitric(V) acid given that

nitric(V) acid boils at 78.2 C and an azeotrope mixture containing 68.2% of nitric(V) acid by mass boils at 121 C and 101 kPa. [3 marks]

(iii) State the changes which occur in the composition of the residual liquid and the distillate when a solution containing 80.0% of nitric(V) acid is continuously distilled.

[2 marks] (iv) What is the volume of an azeotropic mixture of aqueous nitric(V) acid required to

prepare 1 dm3 of a 2 mol dm3 solution of nitric(V) acid? [2 marks] [An azeotropic mixture of aqueous nitric(V) acid has a density of 1.42 g cm3 at 101

kPa.](b) (i) Using the relevant standard electrode potentials in the Data Booklet, determine

whether the corrosion of titanium in an acidic condition is spontaneous. [4 marks] (ii) Explain why titanium is still used as an alloy to make the frames of racing bicycles

and spectacles despite its large negative reduction potential. [2 marks]

7. (a) (i) Titanium occurs in nature as a mixture of five isotopes with percentage abundance as follows.

Relative isotopic mass % abundance46.0 8.0047.0 7.4048.0 73.8049.0 5.5050.0 5.30

Name the method used to obtain the above data. [1 mark]




Deduce the atomic structure of each isotope and calculate the relative atomic mass of titanium. [4 marks]

(ii) Pure titanium is obtained commercially in a two-stage process starting from rutile, TiO2. Rutile is reacted with chlorine gas and coke to yield liquid titanium(IV) chloride, TiCl4, which is then reduced by magnesium. Write the equations for the reactions involved. [2 marks]

(iii) Titanium(IV) chloride is a covalent compound. State what would be observed when it is exposed to moist air. Name the reaction involved and state one use of this reaction. [3 marks]

(b) A solution of [Cu(H2O)6]2+ complex is blue but a solution of [CuCl2] complex is colourless. Explain these observations in terms of electronic configurations. [5 marks]

8. (a) The standard electrode potentials of sodium, magnesium and chlorine are -2.71 V, 2.38 V and +1.36 V respectively. Explain the differences in the oxidation-reduction properties of these elements based on their standard electrode potentials. [7 marks]

(b) A mixture of 3 mol of magnesium oxide and 1 mol of iron(III) oxide is heated with an excess of aluminium powder. (i) Determine the standard enthalpy change and explain the observation of the reaction

that occurs. [7 marks] [Standard enthalpy of formation/kJmol1: MgO = 602, Fe2O3 = 824, Al2O3 = 1670.] (ii) Give one example of the industrial usage of the reaction. [1 mark]

9. (a) An optically active alcohol X produces compound Y on dehydration. Y reacts with bromine in tetrachloromethane to produce compound Z which has the composition by mass: carbon, 22.2%; hydrogen, 3.7%; bromine, 74.1%. (i) Determine the empirical formula of Z. [2 marks] (ii) What is the most likely molecular formula of Z? Give one reason for your answer.

[2 marks](iii) Suggest, with reasons, the structural formulae of X, Y and Z. [5 marks]

(b) 1-Chlorobutane, chlorobenzene and ethanoyl chloride can undergo hydrolysis under suitable conditions. (i) Write an equation for each hydrolysis. [3 marks] (ii) Compare the rates of hydrolysis of these chloro-compounds. [3 marks]

10. (a) Compounds R and S are two isomers with molecular formula C8H10O. R gives off white fumes with thionyl chloride and forms a yellow precipitate with alkaline aqueous iodine but S does not. S dissolves in aqueous potassium hydroxide but R does not. R is synthesised starting from bromobenzene whereas S from 4-ethylaniline. (i) Explain the above observations and write the structural formulae of R and S.

[5 marks] (ii) Write equations for the reactions involved. [2 marks] (iii) Write equations for the synthesis of R. [3 marks]

(b) State the reagents and reaction conditions for the synthesis of 2-hydroxybutanoic acid starting from 1-propanol. Write equations for the reactions involved. [5 marks]


15 Oxford Fajar Sdn Bhd (008974T) 2007


PAPER 1 Section A

1. B Isotopes have the same proton numbers. Since protons are in the nucleus therefore the nuclear charges are the same.

2. C A weak acid will have a stronger conjugate base. Phenol is the weakest acid as it has the smallest Ka value so its conjugate base will be the strongest.

3. B H bonded to O, F, N can form hydrogen bonds between the molecules (eg CH3OH). CH3SH cannot form hydrogen bonds with other molecules, only weak van der Waals force exist between the molecules. Therefore the boiling point of CH3OH is higher than CH3SH.

Q+ Q 4. C Lattice energy is proportional to r+ + r

The ionic compound which has a larger cation and anion charge and a smaller size will have a bigger value of lattice energy.

5. A Hhydration is not needed in the calculation of lattice energy using the Born-Haber cycle. The energies used are (i) atomisation energy, (ii) ionisation energy, (iii) enthalpy of formation and (iv) electron affinity.

6. A rate = k[A]m[B]n Exp. 2 4r k(2a)m(b)n = Exp.1 r k(a)m(b)n

m = 2 Exp. 3 r k(a)m (2b)n = Exp. 1 r k(a)m(b)n

n = 0 rate = k[A]2

7. B The reaction is exothermic. Decrease in temperature shifts the equilibrium to the right. Therefore, the yield of SO3 increases.

8. C MX is precipitated when MNO3 is added to X , Y , Z . This shows that MX has the lowest Ksp. MZ is precipitated and MY dissolves when NaZ is added to MY precipitate. Therefore, MZ has a lower Ksp compared to MY.

9. B The strength of ionic bond depends on the difference in electronegativity between the atoms rather than the sizes of the ions. The bigger the difference in electronegativity, the stronger the ionic bond. A stronger ionic bond is formed between a bigger

cation and a smaller anion (eg KF). A smaller cation and a bigger anion form a weaker ionic bond. The compound will be ionic with covalent characteristic (eg BeO).

10. C PV = nRT 150 103 1 103 = n 8.31 (273 + 727) n = 0.018 (total number of moles) PCl5 PCl3 + Cl2

Compound PCl5 PCl3 Cl2Initial mole 0.013 0 0

Reacted x

Formed x x

At equilibrium 0.013x x x

Total number of moles = 0.013 x + x + x 0.018 = 0.013 + x x = 0.018 0.013 = 0.005 PCl2 = PT XCl2 (X Cl2 is mole fraction)

= 150 kPa x 0.005/0.018 = 42 kPa

11. D The Periodic Table is built based on proton number. The elements are divided to blocks s, p, d and f (4 blocks). There are 18 groups and 7 periods.

12. B Kc only changes with temperature.

[SO3]2

13. D Kc = [SO2]2[O2]

(4.6/2)2 = (0.50/2)2(0.010/2) = 1.7 x 104

14. A Sodium. In the mercury cell at the cathode Na/Hg amalgam is produced which upon treatment with water forms NaOH and hydrogen. In the diaphragm cell, at the cathode, hydrogen is produced. At the anode for both cells, chlorine gas is produced.

15. C M1V1 = M2V2

0.050 100 Concentration of acid, M2 = 150 = 0.033 0.20 50 Concentration of salt, M2 = 150 = 0.067 [salt] pH = log Ka + log [acid] 0.067 = log 1.7 105 + log 0.033 = 5.1

OH O

+ H+

conjugate base




16. B 7N2 has 1s22s22p5 has 1 unpaired electron.

8O has 1s22s22p4 has 2 unpaired electrons.

12Mg+ has 1s22s22p63s1 has 1 unpaired electron.

21Sc has 1s22s22p63s23p63d14s2 has 1 unpaired

electron.

17. B Grignard reagent is used to prepare alcohols by reacting it with carbonyl groups. It is prepared by reacting a haloalkane with magnesium in dry ether.

18. D 2H2O + 2e H2 + 2OH

2Cl Cl2 + 2e

2H2O O2 + 4e + 4H+

H2 Cl2 O2

No. of moles of e 2 2 4

Ratio 2 2 1

19. D Raoults Law: PA = XA PAo (XA is mole fraction of A in the miscible liquid mixture,

PAo is the pure vapour pressure of A) PX = XX PXo = 0.30 48 = 14.4 kPa PY = XY PYo = 0.70 36 = 25.2 kPa PT = PX + PY = 14.4 + 25.2 = 39.6 kPa Since the calculated pressure using Raoults law is the

same as the given pressure, the mixture is an ideal mixture. Therefore, the strengths of intermolecular forces of X and Y are the same.

20. A Titanium ion should be able to form bonds with the alkene. Therefore, it must have empty d orbitals.

21. C [Fex(en)2(SCN)2]+ en has 0 charge

SCN has 1 charge x + 2(0) + 2(1) = +1 x = +3 [Fey (EDTA)]2 EDTA has 4 charge y + (4) = 2 y = 2 + 4 = +2

22. A Iodine is black, solid and has weak oxidising power. Since astatine is below iodine, astatine has similar properties.

23. D PbCl4 undergoes hydrolysis as it has d orbitals.

24. D Both Al2O3 (amphoteric oxide) and Cl2O7 (acidic oxide) react with NaOH(aq). However, Cl2O7 reacts with NaOH to form ClO4

(aq) which oxidises Fe2+(aq), green solution, to Fe3+(aq), yellow solution.

25. A When NaCl is added to AgNO3, AgCl forms as a precipitate which dissolves in ammonia. When KI is added, AgI is formed as AgI has a smaller Ksp. The AgI precipitate formed is more than AgCl.

26. C Photochemical smog is formed by the reaction between hydrocarbons (automobile exhaust) and nitrogen dioxide (NO2) in the presence of sunlight.

Eg: N2 + O2 2NO exhaust gas NO is oxidised by air to NO2 which causes smog: 2NO + O2 2NO2

27. D 4 mol NH3 = 4 mol NO Therefore, 1 mol NH3 = 1 mol NO = 1 mol NO2 3 mol NO2 = 2 mol HNO3 Therefore, 3 mol NH3 = 2 mol HNO3 1 mol NH3 = 2/3 mol HNO3 = 2/3 100 = 67%

28. A X must be acid chloride as only acid chloride, when reacted with water, will form white fumes of hydrogen chloride.

29. C optically active the carbon atom has 4 different groups

forms yellow precipitate with iodine solution, therefore alcohol must have

30. D 2-hexene contains a C=C bond which decolourises KMnO4 solution. Benzene does not react with KMnO4.

31. D Alkylbenzene can be oxidised to benzoic acid by KMnO4/H

+.

32. C A nucleophile is an ion or molecule which has a pair of electrons which can be donated.

33. D For a condensation homopolymer, the monomer has 2 different functional groups at both ends which can react to eliminate small molecules such as water or HCl. Example: HO-(CH2)n-COOH or H2N-(CH2)n-COOH

34. C Numbering must start from the aldehyde group CH3C(CH3)=CHCH2CH2C(CH3)=CHCHO 8 7 6 5 4 3 2 1 3,7-dimethyl-2,6-octadienal

35. C Carbonyl groups which have CH3 | CO

gives a positive

iodoform test. The only aldehyde which gives a positive test is ethanal, CH3CHO.

CH = CH2

H | COH group | CH3

OH | CCH3 | H

optically active C atom

can react with alkaline iodine solution to form yellow precipitate

H2O

CH2CI

AICI3COOH

KMnO4

H3O+

CH3




36. C X undergoes elimination reaction with alcoholic sodium hydroxide, forming Y which is an unsaturated hydrocarbon since it absorbs hydrogen gas. Therefore X must be a haloalkane.

PV=nRT 1.1 105 x 210 106 = n x 8.31 298 23.1 n = 8.31 298 n = 0.00933 Y absorbs 0.00933 mol H2

No. of moles of X = 1.75/175 = 0.01 0.01 moles of X forms Y which absorbs 0.00933

moles hydrogen. 1 mole of X forms Y which absorbs approximately 1 mole of hydrogen therefore Y must have 1 double bond.

A and B form triple bonds and D does not undergo elimination reaction.

37. A Hydrocarbons undergo free radical and catalytic cracking reactions.

38. C X is a phenol since it reacts with sodium hydroxide and sodium and also a weak acid.

39. B The polymer is a addition copolymer. Its monomers are

Since the polymer has a double bond, it is elastic and can be vulcanised. It is not thermally stable.

40. B Glycine, NH2CH2COOH, has a base and acid group. The acid group reacts with NaOH forming structure A. The base group can react with HCl forming structure C. The base group can also react with CH3COOH forming structure D. B is formed when the acid group reacts with alcohol forming an ester by the condensation process.

PAPER 1 Section B

41. C Convergence limit is from n=1 to n=. f4 can be used to calculate the energy difference between n=3 and n=2 and f5 to calculate the energy difference between n=4 and n=2 by using the equation E=hf.

The difference in the energy between the two gives the energy difference between n=3 and n=4.

42. D 25X: [18Ar]3d54s2. X is in block d. Hence it has

high density, forms coloured compounds and the highest oxidation number is +7 where all the valence electrons, 3d54s2, is removed.

43. D X(g) + Y(g) Z(g) H = (+)ve According to Le Chateliers Principle an increase in

temperature shifts the equilibrium to the side where the increase in heat is absorbed. The graph shows that Kp is higher with an increase in temperature (1/T 0). Therefore the reaction is endothermic as the equilibrium shifts to the right as the Kp becomes higher with the increase in temperature. Thus the amount of Z increases.

According to Le Chateliers Principle an increase in pressure shifts the equilibrium to the side where the increase in the pressure is absorbed (to the side with less number of moles). Since the right side has less number of moles (1 mole) compared to the left (2 moles), therefore the increase in pressure shifts the equilibrium to the right forming more Z.

44. C T1 is of lower temperature, hence more molecules have lower energy. The activation energy for T1 and T2 are the same as activation energy does not depend on temperature. The number of molecules for T1 and T2 are the same.

45. D Doping (adding of impurities) increases the electrical conductivity of silicon. The impurities can be from Group 13, for example boron which has one valence electron less compared to silicon which is in Group 14. This type of semiconductor is known as p-type semiconductor.

The impurities can be from Group 15 which has an extra valence electron compared to Si, for example phosphorus which has an extra electron compared to silicon. This is known as n-type semiconductor. Since silicon is a semiconductor, its electrical conductivity can be increased by increasing the temperature.

46. C Beryllium and aluminium have diagonal relationship and also Be2+ and Al3+ have similar charge density. Hence the properties of beryllium is similar to aluminium.

47. D A catalytic converter converts the toxic gases, CO, NO and unburned hydrocarbons from the exhaust of vehicles to non-toxic gases such as carbon dioxide and nitrogen.

48. A

OH is a stronger electron donor than CH3 , therefore it determines the position of the entering electrophile,

H H | |C C | | H

+ CH2=C(CH3)CH=CH2

OH OH

C6H12O

H2/Pt

OH

CH3

p-methylphenol

H H | |CCH | | H CI

NaOH/ethanolCH=CH2 + HCI

H2

CH2CH3X

Cl

Y




bromine. Bromine can enter the positions 2, 4, 6 relative to OH. Since position 4 is occupied by CH3, therefore bromine takes up positions 2 and 6 relative toOH.

49. A The reduction of nitrobenzene forms aniline and the reduction of nitrile, CN forms primary amine.

50. C LiAlH4 reduces ester to alcohol but it does not reduce the double bond to alkane.

Saponification breaks the ester bond, O | CO

, forming the salt COONa+ and alcohol.

Aqueous bromine reacts with the double bond forming, OH Br

| | CC

PAPER 2 Section A

1. (a) (i) Fe (ii) X has free-moving (or mobile, or delocalised)

electrons (iii) X has a higher electrical conductivity than

potassium because X has more valence electrons (or delocalised 3d and 4s electrons).

1 (b) (i) O2 (g) O(g) 2

(ii) +742.5 / 3 = + 247.5 kJ mol1

(iii) H4 = 2(1st IE + 2nd IE + 3rd IE)

= 2(762 + 1560 + 2960) = + 10 564 kJ (iv) Lattice energy of X2O3 is higher than that of

XO because the cationic charge of X in X2O3 is higher and the ionic radius of X3+ is smaller than that of X2+.

2. (a) (i) 1s2 2s2 2p6 3s2 3p3

(ii)

(iii) 2p or 3p (iv) Tetrahedron/tetrahedral

(b) (i) Ionic bond (ii) XY or X 2+Y 2

(iii) High melting / boiling point, conducts electricity in molten or aqueous state, colourless / white, soluble in water / insoluble in organic solvent

(Any two of the physical properties above) (iv) Size of X 2+ is smaller than Na+ and the charge

of X 2+ is higher than Na+.

3. (a) (i) PbO(s) + 2HNO3(aq) Pb(NO3)2(aq) + H2O(l) (ii) Basic property (iii) PbO2(s) + 4HCl(l) PbCl2(s) + Cl2(g) + 2H2O(l) (iv) +4 to +2 (v) Oxidising agent

N+ = NCIO2N or N= N+CIO2N

or N2CIO2N or N2+O2N

or N = N+O2N

N = N O2N

OH

(vi) Lead(II) is more stable

(b) (i) S4O62 < I2 < H2O2

(ii) A brown solution is formed as I is oxidised to I2.

(iii) A purple solution will be formed in the CCl4 layer.

4. (a) (i) X

Y

Z

(ii)

(iii) Z is acidic

(b) (i) 2-aminobutane-1, 4-dioic acid

(ii)

(iii) Ionic bond (iv) Chromatography / electrophoresis

PAPER 2 Section B

5. (a) (i) X: 1s2 2s2 2p6 3s2 3p6 4s2 3d7

Aufbaus principle: electrons occupy orbitals with the lowest energy level first

Energy levels: 1s < 2s < 2p < 3s < 3p < 4s < 3d (ii) Nickel or iron Electrons are filled into 3d orbitals. Hence,

effective nuclear charge remains almost

or N = N

OH

O2N

NH3CIO2N or NH3+O2N

NH3+CI + NaOHO2N NH2 + NaCI

+ H2OO2N

H H O H H | | || | |HNCCNCCOOH | | CH2 CH2 | | COOH COOH

H H | | HNCCOOH | CH2 H | | CNCCOOH || | | O H CH2 | COOH

3px




constant because the increase in nuclear charge and the screening effect cancels each other.

(b) (i)

time 0 10.0 20.0 30.0 40.0 50.0 60.0

x 1010 8.4 6.6 5.3 4.2 3.5 2.8 2.1

In 20.9 21.1 21.4 21.6 21.8 22.0 22.3

(ii) k = ln 2 / t1/2 or 0.693 / 30.0 = 0.0231 min1 or 3.85 x 104 s1

(iii) [PAN]90 = 1.05 x 1010 mol dm3

6. (a) (i) Interaction between pure nitric acid with water is stronger than the interaction between pure nitric(V) acid molecules and between pure water molecules. Consequently, vapour pressure is lower than expected according to Raoults Law for ideal solution.

(ii)

(iii) The distillate is pure or 100% nitric(V) acid, the concentration of nitric(V) acid in the residual liquid will continue to decrease until an azeotropic mixture of 68.2% nitric(V) acid is reached.

(iv) Mr of HNO3 = 63 1 dm3 of 2 mol dm3 HNO3 contains 2 mol

(2 63 g) of HNO3. 100 g of azeotropic mixture contains 68.2 g

of HNO3. Mass of azeotropic mixture that contains

(2 63 g) of HNO3

(2 63) 100 = 68.2 Mass (2 63) 100 Density = 1.42 = = Volume 68.2 Volume

Volume = (2 63.0 100) / (1.42 68.2) = 130 cm3

(b) (i) O2 + 4H+ + 4e 2H2O E = +1.23 V

2Ti 2Ti2+ + 4e E = +1.63 V

O2 + 4H+ + 2Ti 2Ti2+ + 2H2O E = +1.23 +

(+1.63) V = +2.86 V The positive E value shows that the reaction

is spontaneous. (ii) It is light (or it has low density). The presence of the TiO2 layer protects the

underlying Ti from corrosion.

7. (a) (i) Mass spectroscopy No. of protons = 22 No. of neutrons = 24, 25, 26, 27 and 28

respectively (46.0 8.00) + (47.0 7.40) + (48.0 73.80) + (49.0 x 5.50) + (50.0 5.30) Ar = 100 = 47.9 (ii) TiO2 + 2Cl2 + C TiCl4 + CO2 TiCl4 + 2Mg Ti + 2MgCl2 (iii) White fumes of HCl are produced due to the

hydrolysis of TiCl4 Uses: Smoke grenades / smoke bombs (b) Cu+ : 3d10

Cu2+: 3d9

Splitting of 3d orbitals occurs in Cu2+ ion. In Cu2+ there is a d-d transition or an electron from a low 3d level absorbs energy and jumps to a higher 3d level. In Cu+ there is no d-d transition.

8. (a) The negative values of E show that sodium and magnesium are reducing agents.

Na Na+ + e E = 2.71 V Mg Mg2+ + 2e E = 2.38 V Sodium is a stronger reducing agent than

magnesium. Therefore, E of sodium is less than E of magnesium.

The positive E value shows that chlorine is an oxidising agent.

Cl2 + 2e 2Cl E = +1.36 V

(b) (i) 3MgO + 2Al 3Mg + Al2O3 3 x (-602) 0 0 1670

H = (1670) 3(602) = +136 kJ

Fe2O3 + 2Al 2Fe + Al2O3 824 0 0 1670

H = (1670) (824) = 846 kJ Observation: Molten metal is formed. Explanation: The aluminium does not react

with magnesium oxide because magnesium is more reactive than aluminium and the reaction is endothermic. Aluminium reacts with ferum(III) oxide because aluminium is

0 20 40 60 80 100

20.921.021.1

In[PAN] or

[PAN]x1010

mol dm3

t'1/2 = t "1/2 First order reaction

time/min

vapour

liquid liquid

vapour

100

0 100

121Boiling point/C

% composition of HNO3

78.2

68.2%

time/mint "1/2t'1/2




more reactive than ferum and the reaction is exothermic.

(ii) Welding

9. (a) (i)

Element C H Br

Percentage 22.2 3.7 74.1

No. of moles 22.2/12= 1.85

3.7/1= 3.7

74.1/80= 0.93

Ratio 1.85/0.93= 2

3.7/0.93= 4

0.93/0.93= 1

Empirical formula: C2H4Br (ii) C4H8Br2 When addition reaction occurs, two bromine

atoms are added to a double bond to form a dihaloalkane (dibromoalkane).

(iii) Y is alkene or Y has double bond after dehydration.

X has chiral C atom because it is optically active.

X is CH3CH(OH)CH2CH3. Y is CH3CH=CHCH3. Z is CH3CHBrCHBrCH3.

(b) (i) CH2ClCH2CH2CH3 + OH reflux

CH2(OH)CH2CH2CH3

Cl + OH 200 atm, 300 C O

CH3COCl + H2O cold CH3COOH + HCl

(ii) Cl < CH2ClCH2CH2CH3 < CH3COCl

Cl is least reactive because of delocalised electrons in the benzene ring (or because of

overlapping of p orbital of Cl atom with C atom of benzene ring). CH3COCl is most reactive because C=O is an electron-withdrawing group.

10. (a) (i) R is an alcohol because it gives off white fumes with thionyl chloride.

R has CH3CH(OH) group because a yellow precipitate is formed with alkaline aqueous iodine.

S contains phenol group because it dissolves in KOH.

R is CH(OH)CH3

S is HO CH2CH3

(ii) CH(OH)CH3 + SOCl2

CHClCH3 + SO2 + HCl

CH(OH)CH3 + I2 + OH

CHI3 + COO

(iodoform)

HO CH2CH3 + KOH KO CH2CH3 + H2O

(iii) Br + Mg dry, ether

MgBr

MgBr + CH3CHO

CH3COMgBrH

CH3COMgBrH

+ H2O H+ (aq)

CH3COHH

(b) CH3CH2CH2OH Cu CH3CH2CHO

CH3CH2CHO + HCN or NaCN/H+ CH3CH2CH(OH)CN

CH3CH2CH(OH)CN + H+ + 2H2O

CH3CH2CH(OH)COOH


actual 2006 stpm chemistry

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