HWA CHONG INSTITUTION

C2 PRELIMINARY EXAMINATION

Higher 2 CHEMISTRY 9746 PAPER 1

20 Sept 2007 1 hour

Do not open this booklet until you are told to do so.

INSTRUCTIONS TO CANDIDATES 1. Check that there are 17 printed pages in this question booklet. 2. Fill in your particulars on the optical mark sheet. Enter your NRIC number or FIN

number and shade accordingly. 3. There are forty questions in this paper. Answer ALL questions. For each question,

there are four possible answers, A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the Optical Mark Sheet provided.

4. After the examination, you are required to submit only the optical mark sheet.

INFORMATION FOR CANDIDATES Each correct answer will score one mark. Marks will not be deducted for wrong answers.

A Data Booklet is provided. You may use a calculator.

Any rough working should be done in this booklet.

This question booklet consists of 17 printed pages

C2 Prelim 2007 9746/01/HCI 2

Section A

1 Which of the following is a possible configuration of a stable M3+ ion in the ground state?

A 1s2 2s2 2p3

B 1s2 2s2 2p6 3s2 3p1

C 1s2 2s2 2p6 3s2 3p6 3d2

D 1s2 2s2 2p6 3s2 3p6 3d2 4s2

2 Wines often contain a small amount of sulphur dioxide that is added as a preservative. The sulphur dioxide content of a wine is found by the following method: A 50 cm3 sample of white wine is reacted with 40.0 cm3 of 0.01 mol dm−3 of excess aqueous iodine. The sulphur dioxide in the wine is oxidized to sulphate, SO4

2−, in the process. The unreacted iodine requires exactly 23.60 cm3 of 0.02 mol dm−3 sodium thiosulphate for complete reaction. Determine the concentration of sulphur dioxide, in mol dm−3, in the wine.

A 1.64 x 10−3 B 3.28 x 10−3 C 4.72 x 10−3 D 9.44 x 10−3

3 In which of the following pairs of compounds (i) does the first compound have a larger bond angle about the central atom than

the second compound and, (ii) is the second compound more polar than the first compound?

A CO2, BeCl2

B IClF2, ClO2

C SO2, HCN

D BCl3, NO2

4 Three vessels containing 90 cm3 of iodine fumes, 4 dm3 of argon and 0.01 m3 of water vapour respectively at 150oC and 101 kPa were connected together. The connected vessels were allowed to cool to room temperature. What was the final pressure in the connected vessel?

A 20.2 kPa C 28.7 kPa

B 71.1 kPa D 70.7 kPa

C2 Prelim 2007 9746/01/HCI 3

5 Which graph correctly describes the behaviour of fixed masses of the ideal gases L and M

where the number of moles of L is greater than number of moles of M?

A

B

C

D

6 Figure 1 shows the first eight ionisation energies of an element G while Figure 2 shows

the boiling points of eight consecutive elements (including G). With reference to Figure 2, which of the options, A, B, C or D corresponds to the boiling point of element G?

pV

T0

M

L

constant V

Figure 1 Figure 2

Ioni

satio

n En

ergy

/ kJ

mol

−1

Boi

ling

Poin

t / o C

Number of electrons Atomic Number

AB

C D

pV

p1

constant T

M

L

0

V

p1

0

M L

constant T V

T

constant P

M

L

0

C2 Prelim 2007 9746/01/HCI 4

7 The table below gives the standard enthalpy change of hydrogenation of three compounds to form cyclohexane:

Compound ΔHhydrogenation /kJ mol−1

benzene −206

1,3,5−cyclohexatriene −360 cyclohexene −120

Which of the following statements is correct?

A 1,3,5−cyclohexatriene is more stable than benzene.

B Benzene has a lower energy content than 1,3,5−cyclohexatriene.

C The C=C bond energy in cyclohexene is weaker than that in 1,3,5−cyclohexatriene.

D The enthalpy change of atomisation of benzene is smaller than that of 1,3,5−cyclohexatriene.

8 A student dissolved 8.4 g of sodium fluoride in 250 g of water. Given the following thermodynamic data, Lattice energy of NaF −918 kJ mol−1

Enthalpy change of hydration of F − −457 kJ mol−1

Enthalpy change of hydration of Na+ −390 kJ mol−1

what would be the initial temperature of the water if the final temperature of the solution is 20.00oC? Assume that the specific heat capacity of sodium fluoride solution is 4.2 J g−1 K−1.

A 6.48 oC B 19.99 oC C 20.01 oC D 33.52 oC

9 Two colourless substances, X and Y, react to give a coloured substance Z. The times, t, taken for various initial concentrations of X and Y to produce Z are recorded below.

[X]/ mol dm−3 [Y]/ mol dm−3 t/s

0.05 0.05 44

0.05 0.10 22

0.10 0.05 44

What is the rate equation for the reaction?

A rate = k[Y] B rate = k[X][Y]

C rate = k[Y]2 D rate = k[X][Y]2

C2 Prelim 2007 9746/01/HCI 5

10 The mechanism for the production of nitrosyl bromide, NOBr, from nitrogen monoxide and bromine is thought to be as follows.

NO + Br2 NOBr2 (fast) NOBr2 + NO → 2NOBr (slow)

Which of the following rate equations is consistent with the mechanism?

A rate = k[NOBr2][NO] B rate = k[NO]2[Br2]

C rate = k[NO][Br2] D rate = k[NO][Br2]2

11 The use of Data Booklet is relevant to this question. Peroxodisulphate ions convert iodide ions into iodine slowly.

S2O8

2−(aq) + 2I −(aq) 2SO42−(aq) + I2(aq)

The rate of the reaction can be increased by the addition of catalysts such as aqueous iron(II) ions. A possible catalysed reaction pathway involves the following steps: Step 1 2Fe3+(aq) + 2I −(aq) I2(aq) + 2Fe2+(aq) Step 2 S2O8

2−(aq) + 2Fe2+(aq) 2SO42−(aq) + 2Fe3+(aq)

Which of the following statements is incorrect?

A Fe2+ is a stronger reducing agent than I −.

B S2O82− is a stronger oxidizing agent than Fe3+.

C The Ecell for step 2 is more positive than step 1.

D Aqueous cobalt(II) ions can be used as a catalyst in this reaction.

12 When a dilute sulphate solution of a metal J is electrolysed, the metal J and a diatomic gas K are produced at the cathode and the anode respectively in the molar ratio 2:1. In another experiment, the same quantity of electricity is used to electrolyse a saturated sodium chloride solution and a gas L is evolved at the anode. What is the molar ratio of J : K : L?

A 2:1:1 B 2:1:2

C 4:2:1 D 4:2:3

C2 Prelim 2007 9746/01/HCI 6

13 A mixture containing a 1:2 molar ratio of N2O4 and NO at an initial total pressure of 3 atm was allowed to reach equilibrium.

N2O4(g) + 2NO(g) ⇌ 2N2O3(g)

At equilibrium, the total pressure was reduced to 2.75 atm. What is the numerical value of Kp?

A 0.038 B 0.075

C 0.148 D 0.220

14 A solution contains 1 x 10−3 mol dm−3 of bromide, fluoride, iodide and sulphate ions. Which of the following lead(II) compound will be precipitated first when 0.01 mol dm−3 of lead(II) nitrate is added dropwise into the solution?

compound numerical value of solubility product (at 25oC)

A Lead(II) bromide 4.0 x 10−5

B Lead(II) fluoride 2.7 x 10−8

C Lead(II) iodide 7.1 x 10−9

D Lead(II) sulphate 1.6 x 10−8

C2 Prelim 2007 9746/01/HCI 7

15 The following graphs show the change in pH when four different pairs of acid and base were titrated against each other.

In each titration, a 1.0 mol dm−3 solution of an acid is gradually added to 20 cm3 of a 1.0 mol dm−3 solution of a base. Which of the following pairs of solution could not have given any of the graphs above?

alkali acid

A NH3 HCl

B Ba(OH)2 HCl

C KOH H2SO4

D NH3 CH3CH2CO2H

16 0.093 g of a Group II carbonate was thermally decomposed and the residue was dissolved in 100 cm3 of water. On titrating the solution against 0.03 mol dm−3 HCl, it was found that 31.50 cm3 was required for complete neutralisation. What was the Group II metal in the carbonate?

A Ba B Ca C Mg D Sr

C2 Prelim 2007 9746/01/HCI 8

17 A mixture of iodine and chlorine was reacted with excess sodium thiosulphate solution. The resulting mixture was treated with excess aqueous barium nitrate. Precipitate T formed was filtered off and washed with distilled water. The filtrate was treated with excess silver nitrate. The precipitate formed was filtered off and washed with excess aqueous ammonia. The mixture was again filtered leaving behind precipitate U. The resultant filtrate was treated with aqueous lead nitrate to give a white precipitate V. Which anion was present in each of the precipitates respectively?

Precipitate T Precipitate U Precipitate V

A Cl –

I – NO3–

B I – SO42– NO3

–

C SO42– I – Cl –

D SO42– NO3

– Cl –

18 A heated glass rod was dipped into a jar containing hydrogen chloride, hydrogen bromide and hydrogen iodide. Which of the following observations is correct?

A A strong smell of chlorine was detected.

B Reddish−brown and purple fumes were seen.

C Purple fumes were seen.

D White fumes were seen.

19 Rhodium and its compounds are used as catalysts for many important reactions. Which of the following properties makes rhodium a suitable heterogeneous catalyst?

A Rhodium has vacant d-orbitals of suitable energy.

B Rhodium exhibits variable oxidation states.

C Rhodium is able to form stable complexes.

D Rhodium is able to form coloured compounds.

C2 Prelim 2007 9746/01/HCI 9

20 Aqueous sodium hydroxide was added to a pale green solution of a mixture of two metal cations. The resulting precipitate was treated with excess ammonia solution giving an intense deep blue mixture. The mixture was filtered giving a reddish−brown residue and a deep blue filtrate. The residue was washed with deionised water and treated with excess acidified ammonium thiocyanate giving a blood red solution. Which of the following substances best explains these observations?

reddish−brown residue deep blue filtrate blood−red solution

A Fe(OH)2 Cu(OH)2 [Fe(H2O)6]2+

B Fe(OH)3 [Cu(NH3)4]2+ [Fe(H2O)6]3+

C Fe(OH)2 [Cu(H2O)6]2+ [Fe(H2O)5SCN]2+

D Fe(OH)3 [Cu(NH3)4]2+ [Fe(H2O)5SCN]2+

21 What is the total number of possible stereoisomers that can be formed when the following compound reacts with excess concentrated H2SO4?

OH

ClOH

A 2 B 4 C 6 D 8

C2 Prelim 2007 9746/01/HCI 10

22 Compound Q was subjected to the following tests and the results are recorded below.

reagent and condition observations

Acidified KMnO4, warm Solution turns from purple to colourless. CO2 is evolved.

Fehling’s reagent, warm No precipitate seen.

Tollen’s reagent, warm Silver mirror observed.

Which of the following could be compound Q?

A

O H

CHCH2

B

O CH3

C

O OH

CH2OH

D

H2C

O

H

OH

23 Which sequence shows the correct order of increasing ease of hydrolysis of the following compounds?

COCl

Cl

Cl

Br

R S T U

A T < U < S < R

B T < S < U < R

C R < S < U < T

D R < U < S < T

C2 Prelim 2007 9746/01/HCI 11

24 Compound V is formed from ethanal via a series of reactions below.

O

O

O

O

CH3CH3

V

Which of the following reactions is not represented in the sequence?

A nucleophilic addition

B electrophilic addition

C hydrolysis

D condensation

25 Which of the following statements best explains why fluoroalkanes are the least reactive halogenoalkanes?

A Fluorine is much more electronegative than carbon.

B The F − ion is the most stable halide ion.

C The C–F bond is the most polar carbon–halogen bond.

D The C–F bond is the strongest carbon–halogen bond.

26 Which one of the following will be formed when CH3CH(OH)CH2CH=CH2 is distilled with hot acidified potassium dichromate(VI)?

A CH3COCH2CHO and CO2

B CH3COCH2COOH and CO2

C CH3COCH2CH(OH)CH2OH

D CH3COCH2CH=CH2

CH3CHO → CH3CH(OH)CN → CH3CH(OH)COOH →

C2 Prelim 2007 9746/01/HCI 12

27 Amino acids have comparatively high melting points when compared with other organic compounds of similar mass. Which of the following statements best explains this observation?

A In the solid state, amino acids are held together by strong hydrogen bonds.

B In order to melt an amino acid, strong covalent bonds are broken.

C Amino acids are held together by ionic bonding.

D Amino acids are held in fixed positions in a solid lattice.

28 Which compounds will not be formed in the reaction between ethene and aqueous bromine in the presence of aqueous ammonia?

A CH2BrCH2OH

B CH2(NH2)CH2OH

C CH2BrCH2Br

D CH2BrCH2NH2

O

OH

29 Which of the following inorganic reagent may be used to distinguish between propan–1–ol and propan–2–ol?

A sodium hydroxide

B lithium aluminium hydride

C concentrated sulphuric acid

D alkaline aqueous iodine

30 Which of the following shows the correct order of increasing pKa?

O

OH

Cl

OH

CH3

O

NH2 W X Y Z

A X, W, Y, Z

B W, X, Y, Z

C Z, Y, W, X

D Z, W, Y, X

C2 Prelim 2007 9746/01/HCI 13

Section B

For each of the questions in this section, one or more of the three numbered statements 1 to 3 may be correct. Decide whether each of the statements is or is not correct. (You may find it helpful to put a tick against the statements that you consider to be correct). The response A to D should be selected on the basis of

A B C D

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

No other combination of statements is used as a correct response. 31 The compound sodium borohydride, NaBH4, is commonly used as a source of the hydride

anion for synthetic purposes. Which of the following types of bonding are found in the compound?

1 ionic

2 covalent

3 hydrogen bonding

32 In an experiment, 20 cm3 of an organic compound was sparked with excess oxygen. 80 cm3 of carbon dioxide and 80 cm3 of water vapour were obtained. All gases were measured at the same temperature and pressure. Which of the following molecular formula fit the data?

1 CH3CH2CH2CH3

2 CH3CH2CH2CHO

3 CH3CH2CH2CO2H

33 Which of the following statements explains the trend in the reactivity of the Group II metals with oxygen?

1 The reduction potential of the Group II metals becomes less positive down the group.

2

The valence electrons are found further from the nucleus down the group.

3

The ionisation energies of the valence electrons decrease down the group.

The response A to D should be selected on the basis of

A B C D

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

No other combination of statements is used as a correct response. 34 Which of the following compound undergoes complete combustion in oxygen to give a

positive entropy change? (all reactants and products are in the gas phase)

1 hydrogen

2 ethane

3 methanol

35 Which of the following statements are correct about the effect of a heterogeneous catalyst for a reversible reaction?

1 It increases the forward and backward rate constants.

2 It increases the magnitude of the enthalpy change of reaction.

3 It increases the equilibrium constant.

36 A 20 cm3 solution contains 1 x 10−3 mol dm−3 X+ and 1 x 10−3 mol dm−3 Y2+ metal ions. 7 x 10−4 mol of solid sodium sulphate is added to the solution. The numerical values of the solubility product of X and Y sulphates are 7.4 x 10−7 and 9.1 x 10−6 respectively. What can be deduced from this information?

1 The metal Y sulphate will precipitate out selectively.

2 There are more X+ ions than Y2+ ions remaining in the solution.

3 The solubility products of metal X and Y sulphates will change when 2 g of solid sodium sulphate is added to the solution.

C2 Prelim 2007 9746/01/HCI 14

C2 Prelim 2007 9746/01/HCI 15

The response A to D should be selected on the basis of

A B C D

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

No other combination of statements is used as a correct response. 37 During the Contact process, sulphur dioxide is converted to sulphur trioxide as shown by

the equation below.

2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH = −197 kJ mol−1 The following graph shows how the concentration of the three gases changed when a series of changes was made.

Which conclusions can be drawn from this information?

1 At 20 min, the numerical value of the equilibrium constant, Kc, is 1.56.

2 At 20 min, the pressure of the system was increased by reducing the volume.

3 At 10 min, some sulphur dioxide gas was removed from the system.

SO2

O2

SO3

C2 Prelim 2007 9746/01/HCI 16

The response A to D should be selected on the basis of

A B C D

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

No other combination of statements is used as a correct response.

38 An amalgam is formed when mercury is used to dissolve a metal. The amalgam used in the dental filling is a mixture of mercury and tin, Sn8Hg. The diagram below shows an electrochemical cell between an amalgam filling and a gold inlay.

Some standard electrode potentials are given below.

Sn2+/Sn8Hg −0.13 V

Au3+/Au +1.50 V

Al3+/Al −1.66 V

O2/H2O +1.23 V

Which of the following statements about the amalgam is true?

1 When a piece of aluminum foil is in contact with the amalgam filling, the amalgam filling acts as the cathode.

2 When the gold inlay is in contact with the amalgam filling, the gold inlay acts as the cathode.

3 Sn2+ ions are momentarily discharged when the amalgam filling is in contact with the gold inlay or a piece of aluminum foil.

Sn8Hg

The response A to D should be selected on the basis of

A B C D

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

No other combination of statements is used as a correct response.

39 Vitamin B5 has the following structure.

H3C O

N

OH

O

HOH

HO

CH3 Which of the following statements are incorrect?

1 The carboxylic acid group reacts with CH3NH2 to form an amide.

2 Vitamin B5 reacts with 2 moles of HCN.

3 Vitamin B5 reacts with 3 moles of PCl5.

40 Which of the following compounds will not be detected in the reaction between CH2FCH2F and chlorine gas in the presence of UV light?

1 HCl

2 HF

3 H2

~ End of Paper ~

17C2 Prelim 2007 9746/01/HCI