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Section A [15 marks]

Four suggested answers labelled A, B, C and D are given for each question in this section.

Choose one correct answer, and write it in the space provided at Page 6

1. Which one of the following pieces of information about an element cannot be obtained from mass

spectra

A the relative atomic mass

B the relative masses of the isotopes

C the relative abundance of the isotopes

D the number of isotopes

2. Which of the following contains 1 mol of the stated particles.

A Chlorine molecules in 35.5 g of chlorine gas

B Hydrogen atoms in 1 g of hydrogen gas

C Hydrogen ions in 1 dm3 of 1 mol dm3aqueous sulphuric acid

D Oxygen atoms in 22.4 dm3 of oxygen gas at s.t.p.

3. Which of the following electronic configurations represents an element that forms a simple ion with

a charge of -3?

A 1s22s22p63s23p1

B 1s22s

22p

63s

23p

3

C 1s22s

22p

63s

23p

63d

14s

2

D 1s22s22p63s23p6 3d34s2

4. Which diagram best shows the shapes and relative energies of 2s and 2p orbitals in carbon?

5. MTBE is a constituent of petrol. What is the value of angle P and angle Q in a molecule of MTBE

C

CH3

CH3

CH3

O CH3

Angle P Angle Q

Angle P Q

A 90 180B 104.5 180C 109 104.5D 107 109

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6. Ethanol is much more soluble in water than is ethyl ethanoate. Which statement helps to account for

this?

A A hydrogen bond forms between the hydrogen of the-OH group in ethanol and the hydrogen

of a watermolecule.

B A hydrogen bond forms between the hydrogen of theOH group in ethanol and the oxygen

of a watermolecule.

C Ethanol is a polar molecule, but ethyl ethanoate isnon-polar.

D Ethanol is able to dissociate into hydrogen ions and ethoxide ions but ethyl ethanoate is not

able to dissociate

7. The Lewis structures of molecules HF, H2O and NH3are shown respectively below.

Which statement about the molecules is true?

A HF and H2O molecules are planar.

B H2O molecule is a stronger Lewis base than NH3 molecule.

C The boiling points of the molecules increase in the order of H2O, HF, NH3.

D The hydrgen bonds formed by the molecules decrease in the order of HF, H2O, NH3.

8. A small spacecraft of capacity 10m3is connected to another of capacity 30 m3. Before connection,

the pressure inside the smaller craft is 50 kPa and that inside the larger is 100 kPa. If all

measurements are made at the same temperature, what is the pressure in the combined arrangement

after connection?

A. 75 kPa B. 87.5 kPa C. 100 kPa D. 125kPa

9. The phase diagram for iodine is shown below

Which of the following statements is true?

A The line OC represents the effect of pressure on the melting point of iodine.

B Point C is the critical temperature.

C At point B, solid iodine and liquid iodine exist in equilibrium.

D Iodine sublime when heated from room temperature to 120 C at constant pressure of 14 kPa.

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10. The following reaction is fi

If the rate constant doubles

conditions will give the gre

[P]/mol dm-3

[Q] / mol dm3

Temperature/C

11. The reaction of acidified, a

2 I-(aq)

is thought to involve the fol

Which one of the following

A The iodide ion is o

B The acid acts as a c

C The reaction is first

D The rate determinin

12. The percentage of ammoniaplotted against the operatin

following correctly represe

13 Each of the following equili

(i) the pressure is reduced at cons

For which equilibrium will

A H2 (g) + I2(g)

B 4 NH3 (g) + 5 O2 (g

C N2(g) + 3H2(g)

D N2O4(g) 2

4

st order with respect to [P] and zero order with r

P + Q products.

for each 10 C rise in temperature, which of the

test rate of reaction?

A B C

0.10 0.10 0.20

0.20 0.30 0.20

40.0 40.0 30.0

ueous potassium iodide with aqueous hydrogen

H2O2(aq) + 2 H+(aq)I2(aq) + 2 H2O (l)

lowing steps:

H2O2+ I- H2O + OI

-(slow)

OI- + H

+ HOI (fast)

HOI + H++ I

- I2+ H2O (fast)

conclusions cannot be drawn from this informati

idised by the hydrogen peroxide.

talyst.

order with respect to the iodide ion.

g step is H2O2+ I-H2O + OI

-.

obtainable, if equilibrium were established duripressure for two temperatures, 400 C and 500

ts the two graphs?

bria is subjected to two changes carried out sepa

ant temperature; (ii) the temperature is increas

oth of these changes result in an increase in the

2 HI (g) H = +53

) 4 NO(g) + 6 H2O(g) H = - 95

2 NH3(g) H = -92 k

O2(g) H = + 57

spect to [Q].

ollowing sets of

D

0.30

0.10

30.0

eroxide

on?

g the Haber process, isC. Which of the

ately:

ed at constant pressure.

roportion of products?

kJ mol-1

J mol-1

mol-1

J mol-1

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14. In aqueous solution, chlorat

ClO

(aq) + H2O (g)

What is the pH value of a 2.

[At 25C, base dissociation

[Ionic product of water,Kw,

A 4.09 B

15. The following equilibrium

Which statement about this

A Addition of H2O will reduc

B HNO3and NO2+are a conju

C The nitric acid acts as an ox

D The sulphuric acid acts as a

5

e(I) ions, ClO, are hydrolysed according to the

HClO (aq) + OH(aq).

00 x 102

mol dm3

solution of sodium chlorate(I

constant,Kb, of ClOis 3.30 x 10

7mol dm

3

is 1.00 x 1014mol2dm6.]

7.52 C 9.22 D

xists in a mixture of concentrated nitric acid and

equilibrium is correct?

the NO2+concentration.

gate acid-base pair.

idising agent.

dehydrating agent.

quation

), NaClO, at 25 C?

9.91

sulphuric acid.

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Name : ____________________________________ Tingkatan : LOWER 6 ____________

Section A

1 6 11

2 7 12

3 8 13

4 9 14

5 10 15

Section B [15 marks]

Answer all questions in this section on the spaces provided

16. (a) Using Rydberg's Equation, the wavelength and the frequency of hydrogen emission spectrum can becalculated quantitatively. Given the Rydberg Equation is

17

22

21

10097.1,111 =

= mRwhere

nnR HH

i. Based on the equation above, calculate the wavelength of last line in Balmer series. [2 marks]

ii. Based on you answer given in (a) i, compare the wavelength given off by the last line in Lyman

Series and explain your answer [2 marks]

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

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

(b) Diagram below shows the emission spectra of hydrogen atom in Lyman series.

P

i. Draw a labelled diagram showing how spectrum P was formed [3 marks]

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17. Grape juice has a pH of 3.75.

(a) i. Define pH. ....................................................................................................................... [1 mark]

ii. Calculate the molar concentration of hydrogen ions in grape juice. [1 mark]

(b) Grape juice can be titrated with standard alkali. A 25.0 cm3sample of grape juice was exactly

neutralised by 27.5 cm3of 0.100 mol dm

-3sodium hydroxide using phenolphthalein as indicator.

Assuming that the acid inside grape juice is monobasic acid, calculate the concentration of acid in

the juice.

[2 marks]

(c) (i) How can you explain the difference between the two results you have obtained in (a) (ii) and (b)

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

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

[2 marks]

(iii) Calculate the dissociation constant of acid. [2 marks]

Section C [30 marks]

Answer any two questionsin this section.

18. (a) The major acidic component of soured milk is lactic acid: CH3CH(OH)COOH. When 10.0 cm3of a

solution of lactic acid was titrated against 0.050 mol dm-3

sodium hydroxide the following pH

readings were obtained:

Volume ofNaOH added

/cm3

0 2 4 6 8 10 12 14 15.9 16 16.1 18 20

pH 2.5 3.1 3.4 3.7 3.9 4.1 4.4 4.7 5.0 9.1 11.4 11.6 11.8

(i) Plot a graph of these results with pH on the y-axis and volume added on the x-axis.Suggest an

indicator, giving a reason for your choice. [5 marks](ii) Calculate the concentration of the lactic acid in the solution. [2 marks]

(iii) Deduce the Kavalue from the graph for lactic acid [1 marks]

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(b) The mass spectrum of rhombic sulphur is shown below

(i) Explain why the mass spectrum of rhombic sulphur consists of a number of peaks [2 marks]

(ii) Identify the species which is most abundant in the sample of sulphur vapour. [2 marks]

(iii) From the mass spectrum, deduce the molecular mass and formula of rhombic sulphur. [2 marks]

(iv) State the other allotrope of rhombic sulphur [1 mark]

19. (a) Bromide ions are slowly oxidised by bromate (V) ions under acidic condition according to the

following equation below

BrO3-(aq) + 6 H

+(aq) + 5 Br

-(aq) 3 Br2(aq) + 3 H2O (l)

Table below shos the results of four experiments under constant temperature

Experiment [BrO3-] / mol dm

-3 [Br

-] / mol dm

-3 [H

+] / mol dm

-3 Initial rate / mol dm

-3s

-1

1 0.400 0.280 0.031 1.29 x10-3

2 0.600 0.280 0.031 1.94 x10-3

3 0.600 0.560 0.031 3.87 x10-3

4 0.400 0.280 0.062 5.16 x10-3

i. Calculate the order of reaction with respect to BrO3-, Br

-and H

+ [7 marks]

ii. Write the rate equation and calculate the rate constant of the reaction [2 marks]

(b) Ozone, O3, may be used as a bactericide in the treatment of waste water. The concentration of ozone

in water may be determined using the following equation:

O3(g) + 3 I(aq)+ 2H+(aq) O2(g) + I3

-(aq) + H2O (l)

In an experiment, 500.0 cm3of a waste water sample was treated with an excess of iodide ions. The

volume of oxygen gas collected from the reaction at 25.0 C and 101.3 kPa was 10.0 cm

3

. Calculatethe concentration of ozone in the waste water sample under the above conditions of temperature and

pressure. [6 marks]

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20.(a) The key reaction during the Contact process for manufacturing sulphuric acid is as follows.

2 SO2 (g) + O2(g) 2 SO3(g) ; H = - 197 kJ mol-1

When a 2:1 ratio of sulphur dioxide and oxygen at a total initial pressure of 3 atm is passed over a

catalyst at 430 C, the partial pressure of sulphur trioxide at equilibrium is found to be 1.9 atm.

i. Calculate the partial pressures of SO2and O2at equilibrium [4]

ii. Calculate the equilibrium constant of partial pressure, Kpof the reaction above. [3]

(b) By drawing Lewis structure, compare the shape and polar properties of sulphur dioxide, SO2and

sulphur trioxide, SO3. [8]

============END OF QUESTION PAPER ===========

Prepared by Approved by

___________________________ ____________________________

[Chew Chin Kuen]

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Section A

1 A 6 B 11 B

2 B 7 D 12 A

3 B 8 B 13 D

4 A 9 A 14 D

5 C 10 D 15 B

16 a)

=

22

7 1

2

110097.1

1

[1]

= 365 nm [1]ii. last line of Balmer series has a shorterwavelength compare to Lyman series [1]-since the energy level difference between n=2

to n = is shorter [1]

b)

17. a) i. pH = -lg [H+] or [H3O+] (insist [ ]) @explain by words [1]ii. 1.78 x 10-4mol dm-3(3 s.f. with unit) [1]b) Ma(25.0) / (0.100)(27.5) = 1/1 [1]Ma= 0.110 mol dm3(3 s.f. with unit) [1]

c) - Grape juice is weak acid / dissociatepartially in water [1]- however, it react completely with NaOH [1]d) Ka= [H3O+]2/ c or subst [1]Ka = 2.88 x 10-7mol dm-3(3 s.f. with unit) [1]

Section C18 a) i. refer graph [3][Axis = 1] [Point plotted = 1] [Curves = 1]- Suitable indicator : phenolphthalein /bromothymol blue [1]- The effective pH range intercepted the endpoint of titration [1]ii. Ma(10.0) / (0.050)(16) = 1/1 [1]

Ma= 0.080 mol dm3

(2 s.f. with unit) [1]iii. Ka = (check graph) (1/2 V of end point) [1]b) i. Since sulphur exist as molecules [1]- Each peak represent fragment of sulphur ionwith different molecular mass (or m/e) [1]ii. most abundant = m/e 64 [1]molecular ion = S2+(ins : +) [1]iii. RMM = 256 [1] molecular formula : S8 [1]

iv. monoclinic sulphur / -sulphur [1]

19 a) i. rate = k [BrO3-]x[Br-]y[H+]z [1](show all 4 substituted rate equation = [3]show 3 substituted rate equation = [2]show 2 substituted rate equation = [1]Exp 1 :1.29 x 10-3= k (0.400)x(0.280)y(0.031)z

Exp 2 :1.94 x 10-3= k (0.600)x(0.280)y(0.031)z

Exp 3 :3.87 x 10-3= k (0.600)x(0.560)y(0.031)z

Exp 4: 5.16 x 10-3= k (0.400)x(0.280)y(0.062)z

Divide Exp 2 / Exp 1 ; x = 1 [1]Divide Exp 3 / Exp 2 ; y = 1 [1]Divide Exp 4 / Exp 1 ; z = 2 [1]ii. rate = k [BrO3-] [Br-] [H+]2 [1]

k = = 12.0 mol-3dm9s-1(3 s.f. with unit) [1]

b) m1 : PV = nRT [1]m2 : (101.3 x 103) (10.0 x 10-6) =

n (8.31) (273 + 25.0) [1]m3 : n = 4.09 x 10-4mol [1]m4 : Since 1 mol of O3 1 mol of O2 [1]m5 : [O3] = 4.09 x 10-4/ (500/1000) [1]m6: = 8.18 x 10-4mol dm-3 [1]

20 a) i. 2 SO2 + O2 2 SO3Initial : 2 atm 1 atm [1]At eq : - 1.9 - (1.9 x ) + 1.9 [1]Px 0.10 atm [1] 0.050 atm [1]ii. [1] [1]

Kp = 7220 atm-1(2/3 s.f. with unit) [1]

20 b) Each correct comparison = 1

SO2 SO3

Lewis

Shape Bent Trigonal planar

No of electron 2 bond pair and 1 lone pair 3 bond pair

Polarproperties

Polar molecule Non-polar molecule

X Axis labelled [1]Show at least 4 energylevel n = 1 to n = 4 [1]Draw the arrow downfrom n = 4 to n = 1 [1]

)050.0()10.0(

)9.1(2

2

=PK)()(

)(

22

3

2

2

OSO

SO

PPP

PK =