2016 Senior External Examination
Chemistry
Paper Two — Question book
Friday 28 October 2016
1 pm to 3:10 pm
Time allowed
• Perusal time: 10 minutes
• Working time: 2 hours
Examination materials provided
• Paper Two — Question book
• Paper Two — Resource book
• Paper Two — Response book
Equipment allowed
• QCAA-approved equipment
• calculator
Paper Two is an open book examination. You may refer to any paper-based
material that you have brought into the examination room.
Directions
You may write in this book during perusal time.
Paper Two has five questions of equal value (attempt four questions only).
Assessment
Paper Two assesses the following assessment criterion:
• Complex reasoning processes
Assessment standards are at the end of this book.
After the examination session
Take this book when you leave.
For all Queensland schools
Planning space
Complex reasoning processes
Paper Two has five questions of equal value.
Attempt four questions only.
If you respond to all five questions, only your first four responses will be assessed.
Write your responses in the response book.
In each response, give full reasoning in terms of your knowledge and application of chemistry
and use of the range of scientific and complex reasoning processes learned during your study of
the subject.
Question 1
Steel often contains small amounts of impurities.
In a quality control analysis for sulfur impurity, a 5.60 g steel sample was burned in a stream of
oxygen and the sulfur was fully converted to sulfur dioxide gas. The sulfur dioxide was then oxidised
to sulphate by using a hydrogen peroxide solution to which 30.00 mL of 0.0400 M sodium hydroxide
had been added.
The equation for the reaction is:
2–
–
SO 2  g  + H 2 O 2  aq  + 2OH  aq   SO 4  aq  + 2H 2 O  l 
It was found that 22.48 mL of 0.0240 M hydrochloric acid was required to neutralise the base
remaining after the oxidation reaction.
Calculate the percentage of sulfur in the 5.60 g sample of steel.
Question 2
A gas bulb assembly is set up as shown below.
Bulb A contains 32 g of CH4 at 127 °C and 2 atm pressure.
Bulb B contains 0.8 mol of argon at 127 °C and has a volume of 20 L.
Bulb A
CH4
Bulb B
Ar
Not to scale
The tap is opened and the unreactive gases are allowed to mix until constant pressure is reached.
The assembly is returned to the same temperature (127 °C).
Calculate the partial pressure of argon after mixing.
1
Question 3
Silver is found in nature as large nuggets, silver ores or with other metals and their ores. An aqueous
solution containing cyanide ion is often used to extract the silver using the following reaction that
occurs in a basic solution.
–
–
Ag  s  + CN  aq  + O 2  g   Ag  CN  2  aq 
Write a balanced equation for the reaction above using either oxidation numbers or half-cell
equations.
Question 4
When 0.1 mole of a weak acid, HB, was dissolved in water and made up to 1.0 litre, pH measurements
showed that 4% of the HB molecules had dissociated.
What percentage of HB molecules will be dissociated if the 1.0 litre solution above is then diluted to
10.0 litres?
Question 5
Analysis of a natural gas sample gave the following percentage composition by volume:
Compound
%
methane (CH4 )
89.5
ethane (C2 H6 )
5.5
nitrogen (N2 )
2.0
propane (C3 H8 )
2.0
carbon dioxide (CO2 )
1.0
Use the following standard heats of formation to calculate the heat change that accompanies the
complete combustion in air of 100.0 L of natural gas at one atmosphere pressure and 25 °C.
Compound
H°f (kJ mole– 1 )
methane
–74
ethane
–84
propane
–103
water
–286
carbon dioxide
–393
End of Paper Two
2
3
Very High Achievement
A high ability to use complex
reasoning in challenging
situations involving the
candidate’s understanding of
subject matter, and a high
ability to use scientific
processes at an advanced
level.
Criterion
Complex reasoning
processes
Sound Achievement
Some success in using
complex reasoning in
challenging situations
involving the candidate’s
understanding of subject
matter, and some success in
using scientific processes at
an advanced level.
High Achievement
Competence in using complex
reasoning in challenging
situations involving the
candidate’s understanding of
subject matter, and
competence in using scientific
processes at an advanced
level.
Paper Two
Limited Achievement
Very Limited Achievement
Assessment standards from the Chemistry Senior External Syllabus 1998 (amended 2006)
© The State of Queensland (Queensland Curriculum and Assessment Authority) 2016
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