2008 CHEMISTRY TRIAL EXAMINATION
Name
: _________________________________
QUESTION
BOOKLET
Student No. : _________________________________
Group
: ______________________________
1
16 pages, 4 questions
Monday 22 September: 11.30 a.m.
Time : 3 hours
Examination material:
Question Booklet 1 (16 pages)
Question Booklet 2 (11 pages)
Question Booklet 3 (13 pages)
Approved dictionaries and calculators may be used
Instructions to Candidates
1.
You will have 10 minutes to read the paper. You must not write in your question booklets during this reading time but
you may make notes on the scribbling paper provided.
2.
You will be expected to extract information such as atomic number and relative atomic mass from the periodic table on
page 3 of Question Booklet 1, which you may remove from this booklet before the examination begins (follow
instruction from invigilator). Tables showing the relative activities of metals and SI prefixes are on page 4.
3.
This paper consists of twelve questions, four in Question Booklet 1, four in Question Booklet 2, and four in Question
Booklet 3:
Question Booklet 1 (Questions 1 to 4)
Answer all parts of Questions 1 to 4 in the spaces provided in this question booklet.
You may write on page 16 if you need more space to finish your answers.
Question Booklet 2 (Questions 5 to 8)
Answer all parts of Questions 5 to 8 in the spaces provided in Question Booklet 2.
You may write on page 11 of Question Booklet 2 if you need more space to finish your answers.
Question Booklet 3 (Questions 9 to 12)
Answer all parts of Questions 9 to 12 in the spaces provided in Question Booklet 3.
You may write on page 13 of Question Booklet 3 if you need more space to finish your answers.
4.
There is no need to fill all the spaces provided; clearly written, well-expressed answers are required. If you delete part
or all of an answer you should clearly indicate your final answer.
5.
The total mark is 200. The 12 questions are of approximately equal value.
6.
Write your name, student number and group in the space provided at the top of this page and on the front covers of
Question Booklet 2 and Question Booklet 3.
7.
At the end of the examination, place Question Booklet 2 and Question Booklet 3 inside the back cover of Question
Booklet 1.
2
You may remove this page from the booklet by using ruler to tear along the dotted-line.
You may refer to the following table, which shows the relative activities of a number of metals, when
answering questions that involve metals:
Metal Activity
K
Most Reactive
Mg
Zn
Ti
Cu
Ag
Least Reactive
You may refer to the following table, which shows SI prefixes, their symbols and their values, when
answering questions that involve the conversion of units:
3
SI prefix
Symbol
giga
mega
kilo
deci
centi
milli
micro
nano
pico
G
M
k
d
c
m
µ
n
p
4
Value
109
106
103
10–1
10–2
10–3
10–6
10–9
10–12
QUESTION 1
(a)
(iv)
Tramadol is an analgesic used for treating moderate to severe pain. It is marketed in Australia
as Tramal. It has chemical structure shown below:
State and explain the shape around the oxygen atom in tramadol as pointed by the arrow.
O
HO
N
(4 marks)
(i)
(iv)
Give the molecular formula for tramadol.
State two anaerobic products that can be produced from tramadol.
(2 marks)
(2 marks)
(ii)
State the observation when tramadol reacts with acidified dichromate solution. Explain.
(b)
Paracetamol or acetaminophen is another widely-used analgesic. It has the structure shown
below,
(2 marks)
(iii)
Tramadol has low solubility in water, therefore it is often treated with strong acid in
order to increase its solubility in water. Explain.
Paracetamol can undergo alkaline hydrolysis at an elevated temperature. Draw the alkaline
products of this reaction.
(4 marks)
(4 marks)
TOTAL: 18 marks
5
6
QUESTION 2
(ii)
Describe the structural unit all silicates have in common.
The structures of two polymers are shown below:
(2 marks)
(iii)
A
(a)
(i)
Draw the structure of silicate anion in beryl.
B
Name the class to which polymer A belongs based on the type of polymerisation used.
(1 mark)
(ii)
Name the functional group present in polymer A.
(1 mark)
(iii) Draw structural formulae for the monomer(s) used to make polymer B.
(2 marks)
(iv)
State whether beryl has high or low melting point. Explain.
(4 marks)
(b)
Silicates are classified as inorganic polymers. Beryl is a silicate with the formula,
BeyAl2Si6O18
(i)
(4 marks)
Calculate the value of y.
TOTAL: 16 marks
(2 marks)
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8
QUESTION 3
(2)
Structural formulae of benzoic acid and naphthalene are shown below:
Identify one possible source of systematic error, and state how this would affect
the experimental value obtained.
(2 marks)
(b)
Benzoic acid
(a)
Naphthalene
A mixture of benzoic acid and naphthalene was dissolved in an organic solvent.
In an attempt to obtain pure samples of both compounds, a separating funnel was used to
separate the mixture. The procedure for the separation is shown in the flow chart below:
In a laboratory, an experiment to determine the enthalpy of combustion of benzoic acid was
carried out. A certain mass of benzoic acid was used to heat 2.00 L of water in an oxygen-bomb
calorimeter.
The data collected during the experiment are shown below:
Initial temperature of water = 26.55ºC
Final temperature of water = 29.14ºC
(i)
Mixture of benzoic acid and naphthalene in organic solvent
Mass of benzoic acid used = 0.914 g
Specific heat capacity of water = 4.18 J g K
Step 1: shake with potassium bicarbonate solution
Use the appropriate data to calculate the heat released, in kJg-1, during the combustion of
this amount of benzoic acid.
Organic layer containing
Aqueous layer
naphthalene
Step 2: First- acidify with concentrated hydrochloric acid
Second- shake with organic solvent again.
Organic layer containing
Aqueous layer
benzoic acid
(3 marks)
(i)
(ii)
The experiment was repeated several times and an average value for the enthalpy of
combustion of 24.5 kJ mol of benzoic acid was obtained.
(1)
State two observations that would be made after the separating funnel was shaken in
Step 1.
State the purpose of calculating an average value for the enthalpy of combustion.
(2 marks)
(1 mark)
9
10
(ii)
Explain why acidification is necessary in Step 2.
(2)
Using the chromatogram, explain why the Rf value for naphthalene is smaller than
benzoic acid.
(2 marks)
(iii)
Samples from organic layer 1 and organic layer 2 were analysed for purity by Thin Layer
Chromatography, using a non-polar stationary phase and the polar organic solvent as the
mobile phase. The chromatogram obtained is shown in the diagram below:
(3 marks)
(3)
Using the chromatogram, evaluate the effectiveness of the procedure for the
separation of the two anti-inflammatory compounds.
Direction of
mobile phase
(3 marks)
TOTAL: 18 marks
Organic layer 1
(1)
Organic layer 2
Calculate the Rf value for naphthalene in organic layer 1.
(2 marks)
11
12
QUESTION 4
(a)
(iii)
The reaction between steam with chlorine shown below is an endothermic one,
2H2O (g) + 2Cl2 (g)
The graph below shows the changes in concentration for HCl and steam at 200 C.
4HCl (g) + O2 (g)
HCl (g)
(i)
Write the equilibrium expression for the above reaction.
Concentration
of
substances
H2O (g)
(1 mark)
(ii)
At 200 C, 2.500 mol of H2O and 3.000 mol of Cl2 were added to an empty 5.20 L
vessel. When equilibrium is achieved, 0.670 mol of O2 was obtained.
Time
Calculate the equilibrium constant for this reaction at 200 C.
t1
(1)
t2
State the change that was made to the system at t1.
(1 mark)
(2)
Complete the graph till the system achieves equilibrium at t2 again.
(4 marks)
13
14
(3 marks)
Credit will be given for answers to part (b) which show clearly written, well-expressed ideas, and
which present accurate and relevant information in a well-organised, logical manner.
You may write on this page if you need more space to finish your answers to Question Booklet 1.
Make sure to label each answer carefully. (e.g. 1(b)(iv) continued).
Your answer should be confined to the space provided and should take approximately 10 minutes.
(b)
If hydrogen chloride is made in the industry by using the reaction above, briefly describe why
a chemical engineer will use a reasonable high temperature to produce HCl in term of yield,
rate and cost.
(8 marks)
TOTAL: 17 marks
15
16
QUESTION 5
A section of protein chain is shown below,
SOUTH AUSTRALIAN MATRICULATION
2008 CHEMISTRY TRIAL EXAMINATION
Name
: _________________________________
QUESTION
BOOKLET
Student No. : _________________________________
Group
: ____________________________________
X
2
11 pages, 4 questions
Write your answers to Questions 5 to 8 in this question booklet.
(a)
(i)
Identify the number of amino acids present in the chain shown.
(1 mark)
(ii)
Circle and name the linkage group between the amino acids of the chain.
(2 marks)
(iii)
Give the structural formula for the amino acid with the highest molecular mass in the
protein chain above.
(2 marks)
(iv)
Circle an atom of the side group of the chain which able to form hydrogen bond with the
partial negative oxygen atom of water molecules.
(1 mark)
2
(v)
QUESTION 6
In term of bonding, area X is not stable. Explain.
A 1.356 g of fertiliser containing ammonium ion as a source of nitrogen, was boiled with 20.00 mL of
1.113 molL-1 NaOH according to the reaction equation below:
NH4+ + NaOH
(2 marks)
When the reaction has completed, it was cooled and titrated against 0.2247 molL-1 HCl. A titre of
17.55 mL was needed.
(a)
(vi)
A + H2O + Na+
Name the piece of glassware used to transfer the 20.00 mL of NaOH.
Enzymes are often proteins. Explain why enzymes are sensitive to changes in pH.
(1 mark)
(b)
Give the identity of A.
(1 mark)
(c)
(3 marks)
(b)
The chemist pre-rinsed the burette with distilled water before filling it with HCl for titration.
State and explain what will happen to the percentage by mass of NH4+ ions in the fertiliser
Hydroxyl group is a functional group commonly found as a side group of amino acid.
Below is a molecule containing hydroxyl group.
(2 marks)
(d)
Identify one random error found in this experiment.
(1 mark)
(i)
Name this molecule systematically.
Credit will be given for the correct use of significant figures in answers to part (e).
(2 marks)
(ii)
(e)
(i)
(1 mark)
Calculate the amount (in mole) of NaOH added to the fertiliser at the start of the analysis.
This molecule has higher boiling point than corresponding alkane. Explain.
(2 marks)
(3 marks)
(ii)
Write an equation for the titration step.
TOTAL: 16 marks
3
(1 mark)
4
(iii)
Calculate the amount (in mole) of NaOH reacted with HCl at the titration step.
QUESTION 7
The conversion of zinc mineral into zinc metal is summarised in the flow chart below:
Mining of Zinc
Crushing of Ore
(3 marks)
(iv)
Mining
site
Froth Flotation
Waste
Minerals
(gangue)
Calculate the amount of NaOH reacted with fertiliser.
ZnS Concentrates
(25% Zn) containing
Cu2+& Ag+
SO2(g)
(2 marks)
(v)
Hence calculate the amount of NH4+ ion reacted with NaOH
Production
of Y
Roasting
Leaching
(1 mark)
(vi)
Calculate the percentage by mass of
NH4+
Powdered
Zinc
ions in the fertiliser.
Refinery
site
Purification
Metal
residues
Electrolysis
(3 marks)
TOTAL: 18 Marks
5
99.98 % of Zn.
6
(a)
Zinc ore must be treated in several steps, before it is in a form suitable for electrolytic
reduction.
(i)
Froth flotation is the first step in the treatment of zinc ore.
(2 marks)
State the purpose of froth flotation.
(2 marks)
(ii)
Froth Flotation is carried out at the mining site rather than the refinery site.
Explain.
(2 marks)
(iii)
The zinc mineral, ZnS, is roasted in air to form another zinc compound and sulfur
dioxide.
Write a balanced equation for this reaction.
(2 marks)
(iv)
The sulfur dioxide produced, is collected instead of being released into the
environment.
State how this step benefits both the environment and the zinc-producing industry.
Benefit to environment:
Benefit to industry:
(2 marks)
(v)
Describe the purification step.
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8
(vi)
QUESTION 8
State how the final product of electrolysis will differ if purification is omitted.
(1 mark)
(b)
(a)
The ZnSO4 solution is electrolysed and zinc is produced at one of the electrodes.
(i)
(i)
State the oxidation number of oxygen in calcium peroxide.
Write a half-equation for the electrode reaction in which zinc is not produced.
(1 mark)
(ii)
(2 marks)
(ii)
Calcium peroxide (CaO2) is a solid peroxide. Calcium peroxide is insoluble in water but will
dissolve in acid to form hydrogen peroxide. It is used as flour bleaching agent in the food
industry.
Write a full equation for the formation of hydrogen peroxide from the reaction of calcium
peroxide with hydrochloric acid.
State the electrode at which zinc is produced.
(2 marks)
(1 mark)
(iii)
(iii)
State the type of reaction for the equation in (ii).
Explain why it is preferable to use an aqueous zinc solution, rather than a molten
zinc compound, as the electrolyte.
(1 mark)
(b)
Sodium perborate can also release hydrogen peroxide, it is often included in laundry detergent
preparations.
(i)
State the function of hydrogen peroxide in the cleaning process.
(1 mark)
(2 marks)
TOTAL: 16 marks
(ii)
Identify a compound which contains chlorine, and which can function in the same way as
hydrogen peroxide.
(1 mark)
(iii)
Hydrogen peroxide can decompose to form oxygen in water.
Write a balanced equation for this reaction.
(2 marks)
9
10
Credit will be given for answers to part (c) which show clearly written, well-expressed ideas, and
which present accurate and relevant information in a well-organised, logical manner.
You may write on this page if you need more space to finish your answers to Question Booklet 2. Make
sure to label each answer carefully. (e.g.8(a)(ii) continued).
Your answer should be confined to the space provided and should take approximately 10 minutes.
(c)
Sodium zeolites are complex silicates used to reduce hardness in water. Sodium
tripolyphosphates also serve the same purpose.
Explain how sodium zeolites and sodium tripolyphosphates can reduce hardness in water. (you
may include equation(s) to assist your explanation)
(8 marks)
TOTAL: 16 marks
11
12
QUESTION 9
SOUTH AUSTRALIAN MATRICULATION
Chromium used in iron, steel, and nonferrous alloys enhances hardenability and resistance to corrosion
and oxidation.
Data below are used to construct a calibration graph which can be used to determine the percentage of
chromium found in steel. The values below are obtained using AAS.
2008 CHEMISTRY TRIAL EXAMINATION
Name
QUESTION
BOOKLET
: _________________________________
Student No. : _________________________________
Group
: ____________________________________
Concentration, ppb
3
13 pages, 4 questions
(a)
Absorbance, %
0
0
20
9.2
40
19.4
60
28.9
80
39.5
State what the abbreviation AAS stands for.
(1 mark)
Write your answers to Questions 9 to 12 in this question booklet.
(b)
In this analysis, iron is present in great quantity.
Explain why the presence of iron will not interfere with the analysis of chromium using AAS.
(3 marks)
2
(c)
(i)
Construct a calibration graph using the data from the previous page.
(2)
By using the graph, determine the concentration of chromium in the 200.0 mL
steel solution in ppb.
(1 mark)
(3)
Convert the concentration in (2) to mgL -1.
(1 mark)
(4)
Calculate the mass of chromium present in 200.0 mL of steel solution.
(2 marks)
(5)
Calculate the percentage of chromium by mass in the steel.
(4 marks)
(ii)
1.234 g of steel was dissolved in concentrated nitric acid. The resultant solution was
transferred into a 200.0 mL volumetric flask and deionised water was added till the
calibration mark of the flask. The solution was then analysed by AAS. Absorbance value
of 15.0% was obtained for the 200.0 mL steel solution.
(2 marks)
(1)
Describe the correct way to add deionised water till the calibration mark after the
flask was ¾ filled.
TOTAL: 16 marks
(2 marks)
3
4
QUESTION 10
(a)
(iv)
Triglycerides are common molecules which can be found in the human body. An example of
such molecules is shown below,
Triglycerides can be classified as saturated or unsaturated.
State and explain whether this molecule is saturated or unsaturated.
(2 marks)
(b)
In the normal cleaning process, removing triglycerides is often a task that can be done easily by
using a detergent aqueous solution containing anionic surfactant. However in dry cleaning, an
organic solvent is used to remove triglycerides.
(i)
(i)
“Anionic surfactants need an alkaline condition to work effectively”. Justify this
statement.
(3 marks)
Draw the structural formula for the alcohol that can be derived from the triglyceride
molecule above.
(ii)
State the polarity of the solvent used and describe how it can remove the triglycerides.
(2 marks)
(ii)
Circle and name the functional group present in the triglyceride molecule above.
(1 mark)
(iii)
(3 marks)
Determine the number of carbon atoms present in the longest fatty acid used to make this
triglyceride molecule.
(1 mark)
5
6
(c)
Detergents also contain other additives to assist the cleaning process such as bleaching agent,
sodium tripolyphosphates, optical brightener and sodium carbonate.
(i)
QUESTION 11
The production of nitric acid in a factory is summarised in the flow chart below:
Sodium tripolyphosphates act as an alkaline buffer in the cleaning process. Write an
equation for this reaction.
(2 marks)
(ii)
NH3
Air
Compressor
Write an equation to show how carbonate ions can provide an alkaline condition for
anionic surfactants to work effectively.
Air
Converter
900 C
Catalyst
Unreacted
Gases
Water
Cooler
NO2
NO2
Absorber
Nitric acid
Air
(2 marks)
TOTAL: 16 marks
The production of NO2 in the converter involves a series of chemical reactions.
(a)
The overall reaction in the converter is exothermic.
(i)
State two raw materials required by this process.
(2 marks)
(ii)
For the reaction to start in the converter, the reactants need to be heated up first. Explain.
(2 marks)
(iii)
Explain why heating is no longer necessary once the reaction has started.
(2 marks)
7
8
(b)
QUESTION 12
Catalyst is an important chemical in this process.
(a)
State and describe the role of catalyst in chemical reaction.
Fuel cell is an alternative source of energy to burning fossil fuels.
Extensive research has been carried out to find a suitable fuel for fuel cell. A group of
researchers is currently using propane as a fuel in their research study.
Oxygen gas
(3 marks)
(c)
H3PO4
Electrolyte
Propane gas
Porous
Electrodes
Write an equation for conversion of NO 2 to nitric acid at the absorber.
(2 marks)
H2O
(d)
Describe one disadvantage for the manufacturer if gases containing NO2 are emitted from the
factory.
(i)
Identify the charge for the electrode where oxygen reacted.
(1 mark)
(2 marks)
(e)
(ii)
State two reasons why porous electrodes is used.
The brown NO2 can also produce colourless dinitrogen tetroxide, N2O4 shown in the reversible
equation below:
2NO2 (g)
(2 marks)
N2O4(g)
At room temperature, an enclosed tube containing these two gases is allowed to reach
equilibrium. The enclosed tube is then placed into a refrigerator at 4 C. The brown colour of the
tube turns lighter. Explain whether the forward reaction is exothermic or endothermic.
(iii)
Overall chemical equation of the cell is shown below,
CH3CH2CH3 + 5O2
3CO2 + 4H2O
Write the half-equations for the reduction and oxidation half-reactions.
Reduction:
Oxidation:
(3 marks)
(4 marks)
TOTAL: 16 marks
9
10
(b)
Zinc-air cell is another type of electrochemical cell. A schematic diagram of the cell is shown
below:
(v)
State the main form of energy produced in this type of electrochemical cell.
(1 mark)
e
(vi)
Air containing
oxygen
KOH
electrolyte
Explain why the zinc---air battery cannot be classified as a fuel cell.
Zn (s)
(2 marks)
TOTAL: 17 marks
Outlet
Electrodes
(i)
State whether the zinc is acting as the anode or the cathode, and give a reason for
your answer.
(2 marks)
(ii)
By using subshell notation, write the electronic configuration for zinc atom.
(2 marks)
(iii)
Complete the half-equation below for the reaction where oxygen is reacted.
O2 +
4OH
+ 2H2O
(2 marks)
(iv)
State one reason why the use of zinc---air battery may be considered as a desirable
alternative to the combustion of fossil fuels to power motor vehicles.
(1 mark)
11
12
You may write on this page if you need more space to finish your answers to Question Booklet 3.
Make sure to label each answer carefully. (e.g.12(a)(i) continued).
13