2012

By:

Section I Part A: someth1ng

Section I Part B: addoil

Section II Forensic Chemistry: someth1ng

Chemist ry

General Instructions

• Reading time – 5 minutes

• Working time – 3 hours

• Write using black or blue pen

Black pen is preferred

• Draw diagrams using pencil

• Board-approved calculators may

be used

• A data sheet and a Periodic Table

are provided at the back of this

paper

Total marks – 100

Section I Pages 2–17

75 marks

This section has two parts, Part A and Part B

Part A – 20 marks

• Attempt Questions 1–20

• Allow about 35 minutes for this part

Part B – 55 marks

• Attempt Questions 21–30

• Allow about 1 hour and 40 minutes for this part

25 marks

• Attempt ONE question from Questions 21–30

• Allow about 45 minutes for this section

Section I

75 marks

Part A – 20 marks

Attempt Questions 1–20

Allow about 35 minutes for this part

Use the multiple-choice answer sheet for Questions 1–20.

1 Which of the following is not a use of ethanol?

(A) Cleaning agent

(B) Fuel

(C) Car coolant

(D) Medical solvent

2 In the condensation polymerisation of β-glucose, which of the following are the product

and the by-product?

(A) Starch and ethanol

(B) Starch and water

(C) Cellulose and ethanol

(D) Cellulose and water

3 A student incorrectly named a substance 4-fluoro-5-bromo-2,2-dichloropentane; what is

most likely the correct name of the substance?

(A) 5-bromo-2,4-dichloro-4-fluoropentane

(B) 1-bromo-2,2-dichloro-2fluoropentane

(C) 5-bromo-2,2-dichloro-4-fluoropentane

(D) 1-bromo-4,4-dichloro-2-fluoropentane

4 Which of the following molecules has the lowest boiling point?

(A)

(B)

(C)

(D)

5 Calculate the heat released by the complete combustion of 0.65 grams of ethanol where t

he molar heat of combustion of ethanol is 1367kJ/mol.

(A) 19.32 J

(B) 19.32 kJ

(C) 96741 J

(D) 96741 kJ

6 Which of the following solutions would most likely turn methyl orange indicator red?

(A) Hydrochloric acid

(B) Sodium hydroxide

(C) Sodium acetate

(D) Sodium chloride

7 Why are all isotopes of Americium-243 radioactive?

(A) Atomic number is below 82

(B) Atomic number is above 82

(C) The proton-neutron ratio is too large

(D) The proton-neutron ratio is too small

8 Which of the following scientists would most likely have said that “all acids contain

replaceable hydrogen”?

(A) Lavoisier

(B) Davy

(C) Arrhenius

(D) Bronsted-Lowry

9 Which of the following is an advantage of using indicator over a pH meter to measure

the acidity of a solution?

(A) Significantly higher accuracy

(B) Relatively more expensive

(C) Does not require calibration

(D) Able to test the pH of a coloured solution

10 What is the purpose of the addition of nitric acid before performing a precipitation test?

(A) A low pH is required for a precipitation to occur

(B) A high pH is required for the precipitation to occur

(C) To remove any chlorides and acetates

(D) To remove any carbonates

11 A student performed a first-hand investigation to determine the molar heat of combustion

of ethanol.

The student calculated the molar heat of combustion to be 876.5kJ/mol but the actual

molar heat of combustion of ethanol is 1367kJ/mol.

Which of the following is most likely a cause for this discrepancy?

(A) Incomplete combustion

(B) More fuel was used to heat the water than the measure mass loss of fuel

(C) Water absorbed heat from surroundings

(D) Insulation of the metal can holding the water caused more heat loss

12. 5mL of 0.1M HCl is diluted to 100mL with water. What is the new pH of the solution?

(A) 1.0

(B) 2.3

(C) 4.6

(D) 5.3

13. Which layer of the atmosphere contains the highest concentration of ozone?

(A) Ionsphere

(B) Exosphere

(C) Stratosphere

(D) Troposphere

14. The images below represent polymer strands of polyethylene:

Which of the following statements is true?

(A) Polymer A has a higher change than Polymer B to be opaque

(B) Polymer A has higher density than Polymer B

(C) Both polymers are soluble in water

(D) Both polymers are chemical resistant

15. Which of the following is not a condition required in the process of catalytic cracking?

(A) 500°C

(B) Presence of oxygen

(C) Presence of a zeolite

(D) Slight pressure

16. Which of the following cannot be produced by an addition reaction involving ethylene?

(A) 1,2-dibromoethane

(B) 1,1-dibromoethane

(C) Ethane

(D) Chloroethane

17. What is the common name of the molecule shown below?

(A) Halon-114

(B) Halon-204

(C) Freon-114

(D) Freon-204

18. What is the general formula for carboxylic acid?

(A) R-COOH

(B) R-OH

(C) R-CHO

(D) R-NHx

19. In the flame test, the presence of which cation would most likely cause a yellow flame?

(A) Sodium

(B) Calcium

(C) Barium

(D) Lead

20. Which of the following can be used to help reduce SO2 emissions from factories?

(A) CH3COOH

(B) Mg(OH)2

(C) NH4Cl

(D) Na

BLANK PAGE

2012 T R I A L H S C E X A M I NAT I ON

Chemistry

Section I (continued)

Part B – 55 marks

Attempt Questions 21–32

Allow about 1 hour and 40 minutes for this part

Centre Number

Student Number

Answer the questions in the spaces provided. These spaces provide guidance for the expected

length of response.

Show all relevant working in questions involving calculations.

Question 21 (3 marks)

(a) During the course of your study, you performed a first-hand investigation to distinguish 2

between unknown solutions of an alkane and alkene. Describe this experiment and

include any relevant chemical equations in your answer.

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(b) Identify the need for a safety precaution (other than safety goggles) to be used in 1

experiment

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Question 22 (5 marks)

(a) Ethylene is a highly reactive compound that can be polymerized into many useful 3

products.

Explain this statement using TWO examples.

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(b) Compare two ways in which ethanol can be produced. 2

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Question 23 (7 marks)

(a) Identify one purpose of using a salt bridge in a galvanic cell. 1

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(b) A student set up a laboratory experiment as shown in the diagram below to investigate 6

the nature of displacement reactions.

Based on your understanding of redox reactions, account for the observations in this

experiment.

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Question 24 (3 marks)

Discuss whether the Bronsted-Lowry theory would define hydrogen carbonate as 3

an acid or base.

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Question 25 (4 marks)

Analytical data have shown that the pH of rain in developing countries is higher than 4

the measurements obtained from industrialized areas such as Central Europe.

Suggest the causes of this difference and explain its impact on the marine environment.

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Question 26 (9 marks)

A student titrated 0.14 M barium hydroxide solution with 22.35mLs of 0.08M nitric acid.

(a) Write a balanced chemical equation for this reaction. 1

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(b) Calculate the volume of barium hydroxide required in this titration. 2

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(c) The student accidentally spilt an excess 13.5mL of barium hydroxide into the mixture. 4

Calculate the pH of the resulting solution.

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(d) The student noticed a liquid spill on the table, but was unsure of its acidic nature. 2

Suggest an appropriate method to clean the spill and justify your choice.

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Question 27 (8 marks)

(a) Draw the structural formula of citric acid. 1

(b) Citric acid is a naturally occurring substance that enhances the sour taste in food. 7

Describe an experiment you can perform for the production of artificial banana flavouring, pentyl ethanoate.

In your answer, you MUST identify and discuss the following:• Reagents used (include relevant chemical equations) • Equipment used (include and label any relevant diagrams)• Safety precautionsNote: You do NOT have to include the purification process in your answer.

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Question 28 (4 marks)

(a) Identify TWO different branches of chemistry. 1

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(b) Briefly outline the role of a named chemist and the chemical principle that the 3 chemist uses.

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Question 29 (6 marks)

Close monitoring of chemical laboratories and waterways is crucial.

(a) Assess the use of atomic absorption spectroscopy (AAS) in monitoring heavy metal 3 ions in natural water bodies.

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(b) Explain why it is important to monitor the reaction vessel used in the Haber process. 3

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Question 30 (6 marks)

(a) Explain the effects of CFCs in the lower stratosphere, using chemical equations to 3 support your answer.

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(b) Since 1987, many international agreements have been made to alleviate the use of 3 CFCs, including the Montreal Protocol. Outline the steps that have been taken to stop the release of CFCs into the atmosphere.

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Section II

25 marks

Attempt ONE question from Questions 31-35

Allow about 45 minutes for this section

Answer parts (a)-(c) of the question in Section II Answer Booklet 1

Answer parts (d)-(e) of the question in Section II Answer Booklet 2

Extra writing booklets are available

Show all relevant working in questions involving calculations.

Pages

Industrial Chemistry (not available)

Shipwrecks, Corrosion and Conservation (not available)

The Biochemistry of Movement (not available)

The Chemistry of Art (not available)

Forensic Chemistry………………………………………………..19-21

Question 31

Question 32

Question 33

Question 34

Question 35

Question 35 – Forensic Chemistry (25 marks)

Answer parts (a)-(c) in Section II Answer Booklet 1.

(a) Identify the molecule shown in the diagram below. 1

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(b) There are many classes of carbon compounds. 4

Outline how alkanes, alkenes, alkanols and alkanoic acids can be distinguished. In your

answer, include relevant chemical equations

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(c) Compare the formation of a glycosidic bond and a peptide bond. 3

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Question 35 (continued)

(d) (i) Identify the technique used to separate amino acids based on their charge to 1

mass ratio.

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(ii) Explain how paper chromatography works and suggest a possible use in 3

forensic chemistry.

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(e) Describe the structure and composition of DNA. 3

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Question 35 (continued)

(f) Assess the value of a range instrumental techniques in the analysis of samples in 7

forensic chemistry. In your answer, refer to at least THREE instrumental techniques.

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End of Question 35

K+

+ e– K(s) –2.94 V

Ba2+

+ 2e– Ba(s) –2.91 V

Ca2+

+ 2e– Ca(s) –2.87 V

Na+

+ e– Na(s) –2.71 V

Mg2+

+ 2e– Mg(s) –2.36 V

Al3+

+ 3e– Al(s) –1.68 V

Mn2+

+ 2e– Mn(s) –1.18 V

H2O + e

––1 H

2(g) + OH

––0.83 V

Zn2+

+ 2e– Zn(s) –0.76 V

Fe2+

+ 2e– Fe(s) –0.44 V

Ni2+

+ 2e– Ni(s) –0.24 V

Sn2+

+ 2e– Sn(s) –0.14 V

Pb2+

+ 2e– Pb(s) –0.13 V

H+

+ e–

–1 H (g) 0.00 V2 2

A

w

2 2

2

2

2

2

2

2

2 2

2

2 2

–

2012 T R I A L H S C E X A M I NAT I ON

ChemistryDATA SHEET

Avogadro constant, N .................................................................. 6.022 × 1023

mol–1

Volume of 1 mole ideal gas: at 100 kPa and

at 0°C (273.15 K) ...................... 22.71 L

at 25°C (298.15 K) .................... 24.79 L

Ionisation constant for water at 25°C (298.15 K), K ................. 1.0 × 10–14

Specific heat capacity of water ..................................................... 4.18 × 103

J kg–1

K–1

Some useful formulae

pH = –log10

[H+

] ΔH = – m C Δ

T

Some standard potentials

2

SO4

2– + 4H

+ + 2e

–SO (aq) + 2H O 0.16 V

Cu2+

+ 2e–

Cu(s) 0.34 V

–1 O2(g) + H

2O + 2e

–2OH

– 0.40 V

Cu+

+ e–

Cu(s) 0.52 V

–1 I2(s) + e

–I

–0.54 V

–1 I2(aq) + e

–I

– 0.62 V

Fe3+

+ e–

Fe2+

0.77 V

Ag+

+ e–

Ag(s) 0.80 V

–1 Br2(l) + e Br

– 1.08 V

–1 Br2(aq) + e

–Br

–1.10 V

–1 O2(g) + 2H

+ + 2e

–H

2O 1.23 V

–1 Cl (g) + e–

Cl–

1.36 V

–1 Cr2O

2– + 7H

+ + 3e

–Cr

3+ + –7 H O 1.36 V

2 7 2 2

–1 Cl2(aq) + e

–

–

Cl–

1.40 V

2+MnO4–

+ 8H+

+ 5e

–1 F (g) + e–

Mn + 4H2O 1.51 V

F –

2.89 V

1H

1.008Hydrogen

2He

4.003Helium

3Li

6.941Lithium

4Be

9.012Beryllium

KEY

Atomic Number 79Symbol Au

Standard Atomic Weight 197.0Name Gold

5B

10.81Boron

6C

12.01Carbon

7N

14.01Nitrogen

8O

16.00Oxygen

9F

19.00Fluorine

10Ne

20.18Neon

11Na

22.99Sodium

12Mg

24.31Magnesium

13Al

26.98Aluminium

14Si

28.09Silicon

15P

30.97Phosphorus

16S

32.07Sulfur

17Cl

35.45Chlorine

18Ar

39.95Argon

19K

39.10Potassium

20Ca

40.08Calcium

21Sc

44.96Scandium

22Ti

47.87Titanium

23V

50.94Vanadium

24Cr

52.00Chromium

25Mn

54.94Manganese

26Fe

55.85Iron

27Co

58.93Cobalt

28Ni

58.69Nickel

29Cu

63.55Copper

30Zn

65.38Zinc

31Ga

69.72Gallium

32Ge

72.64Germanium

33As

74.92Arsenic

34Se

78.96Selenium

35Br

79.90Bromine

36Kr

83.80Krypton

37Rb

85.47Rubidium

38Sr

87.61Strontium

39Y

88.91Yttrium

40Zr

91.22Zirconium

41Nb

92.91Niobium

42Mo

95.96Molybdenum

43Tc

Technetium

44Ru

101.1Ruthenium

45Rh

102.9Rhodium

46Pd

106.4Palladium

47Ag

107.9Silver

48Cd

112.4Cadmium

49In

114.8Indium

50Sn

118.7Tin

51Sb

121.8Antimony

52Te

127.6Tellurium

53I

126.9Iodine

54Xe

131.3Xenon

55Cs

132.9Caesium

56Ba

137.3Barium

57–71

Lanthanoids

72Hf

178.5Hafnium

73Ta

180.9Tantalum

74W

183.9Tungsten

75Re

186.2Rhenium

76Os

190.2Osmium

77Ir

192.2Iridium

78Pt

195.1Platinum

79Au

197.0Gold

80Hg

200.6Mercury

81Tl

204.4Thallium

82Pb

207.2Lead

83Bi

209.0Bismuth

84Po

Polonium

85At

Astatine

86Rn

Radon

87Fr

Francium

88Ra

Radium

89–103

Actinoids

104Rf

Rutherfordium

105Db

Dubnium

106Sg

Seaborgium

107Bh

Bohrium

108Hs

Hassium

109Mt

Meitnerium

110Ds

Darmstadtium

111Rg

Roentgenium

112Cn

Copernicium

PERIODIC TABLE OF THE ELEMENTS

Lanthanoids

57La

138.9Lanthanum

58Ce

140.1Cerium

59Pr

140.9Praseodymium

60Nd

144.2Neodymium

61Pm

Promethium

62Sm

150.4Samarium

63Eu

152.0Europium

64Gd

157.3Gadolinium

65Tb

158.9Terbium

66Dy

162.5Dysprosium

67Ho

164.9Holmium

68Er

167.3Erbium

69Tm

168.9Thulium

70Yb

173.1Ytterbium

71Lu

175.0Lutetium

Actinoids

89Ac

Actinium

90Th

232.0Thorium

91Pa

231.0Protactinium

92U

238.0Uranium

93Np

Neptunium

94Pu

Plutonium

95Am

Americium

96Cm

Curium

97Bk

Berkelium

98Cf

Californium

99Es

Einsteinium

100Fm

Fermium

101Md

Mendelevium

102No

Nobelium

103Lr

Lawrencium

Elements with atomic numbers 113 and above have been reported but not fully authenticated.

Standard atomic weights are abridged to four significant figures.

Elements with no reported values in the table have no stable nuclides.

The International Union of Pure and Applied Chemistry Periodic Table of the Elements (February 2010 version) is the principal source of data. Some data may have been modified