2012 HSC Trial Paper Chemistry
Marking Guidelines
Section I, Part A
Multiple-choice Answer Key
Question
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Answer
C
D
D
C
B
A
B
B
C
D
A
B
C
D
B
B
C
A
A
B
Section I, Part B
Question 21(a)
Criteria
Describes the procedure of the experiment with specific examples
Includes at least one relevant chemical equation
Describes the procedure of the experiment with specific examples
•
•
•
OR
• Includes at least one relevant chemical equation
Marks
2
1
Question 21(b)
Criteria
• Identifies an appropriate safety precaution other than using safety
goggles
AND
• Justifies the reason for their choice
Marks
1
Question 22(a)
•
•
•
Criteria
Identifies the importance of the double bond in ethylene
Describes the polymerization process of ethylene AND includes a
relevant chemical equation
Includes at least two examples of products produced from the
polymerization of ethylene
Identifies the importance of the double bond in ethylene
•
OR
• Briefly describes the polymerization process of ethylene
• Includes one example of a product produced from the polymerization
of ethylene
Marks
2-3
1
Question 22(b)
•
•
Criteria
Compares the production of ethanol by fermentation and hydration
Identifies ethanol can be produced by fermentation and hydration
Marks
2
1
Question 23(a)
•
Criteria
Identifies a purpose of a salt bridge
Marks
1
Question 23(b)
•
•
Criteria
Accounts for the gradual thinning of the zinc strip
Accounts for the development of a reddish-brown solid on the zinc
strip
Marks
5
AND
• Identifies this solid as copper
• Explains why the blue copper (II) solution becomes paler over time
• Uses relevant chemical equations to explain each of these
observations
• Accounts for at least three observations
• Uses relevant chemical equations to explain these observations
• Provides a general description of at least two observations
AND
• Includes relevant chemical equations
• Provides a general description of at least one observation
OR
• Includes relevant chemical equations
3-4
2
1
Question 24
•
•
•
•
•
•
Criteria
States the Bronsted-Lowry definition of an acid and base
Uses a relevant chemical equation to indicate the acidic AND basic
nature of hydrogen carbonate
Identifies hydrogen carbonate as an amphiprotic substance
States the Bronsted-Lowry definition of an acid and base
Uses a relevant chemical equation to indicate the acidic AND basic
nature of hydrogen carbonate
Uses a relevant chemical equation to indicate the acidic AND basic
nature of hydrogen carbonate
Marks
3
2
1
Question 25
Criteria
• Outlines the relationship between pH and acidity
• Identifies the industrial and/or human sources of pH pollutants such
as SO2 and NOx gases
AND
• Relates this to the difference in the pH of rain in developing and
industrialized countries
• Explains possible impacts of increased acidity on the marine
environment
• Identifies the industrial and/or human sources of pH pollutants such
as SO2 and NOx gases
• Provides possible impacts of increased acidity on the marine
environment
Question 26(a)
Suggested answer
Ba(OH)2(aq) + 2HNO3(aq)  2H2O(l) + Ba(NO3)2(aq) (1 mark)
Marks
3-4
1-2
Note: must also include the appropriate states.
Question 26(b)
Suggested answer
Moles of nitric acid
= volume x concentration
= 0.02235L x 0.08M
= 0.001788 moles
Moles of barium hydroxide required
= moles of nitric acid / 2 (refer to the mole ratio in question 26a)
= 0.001788 moles / 2
= 0.000894 moles (1 mark)
Volume of barium hydroxide required
= moles / concentration
= moles of barium hydroxide required / concentration of barium hydroxide
= 0.000894 moles / 0.14M
= 0.006386…L (leave the answer in this form) (1 mark)
Question 26(c)
Suggested answer
Moles of excess (spilt) barium hydroxide
= volume x concentration
= 0.0135L x 0.14M
= 0.00189 moles
Consider: Ba(OH)2(aq)  Ba2+(aq) + 2OH-(aq)
Moles of excess OH= moles of excess barium hydroxide x 2 (refer to the mole ratio in the above equation)
= 0.00189 moles x 2
= 0.00378 moles (1 mark)
Concentration of excess OH= moles / total volume
= moles of excess OH- / (0.02235L + 0.0135L + volume of barium hydroxide
required)
= 0.00378 moles / (0.02235L + 0.0135L + 0.006386…L)
= 0.0895…M (leave the answer in this form) (1 mark)
Concentration of excess H+
= (1x10^-14) / concentration of excess OH= (1x10^-14) / 0.0895…M
= 1.117…x10^-13M (leave the answer in this form) (1 mark)
pH of resulting solution
= -log(concentration of excess H+)
= -log(1.117…x10^-13M)
= 12.95 (2dp) (1 mark)
Question 26(d)
•
•
Criteria
Identifies the need for a weak, amphiprotic substance to neutralize the
spill
Suggests an appropriate substance such as sodium hydrogen
carbonate
Marks
1-2
Question 27(a)
(1 mark)
Question 27(b)
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Criteria
Identifies ALL the reagents used including 1-pentanol, ethanoic acid,
concentrated sulphuric acid (catalyst) and boiling chips (optional)
Includes the chemical equation for this esterification process (ie. 1pentanol + ethanoic acid  water + pentyl ethanoate)
Provides a correctly labeled diagram of the process
Describes the esterification procedure
Explains the purpose of refluxing
Explains the purpose of the water bath
Explains the need for safety precautions such as gloves and safety
goggles, and performing the experiment in a fume cupboard
Identifies some of the reagents used
Includes the chemical equation for this esterification process
Provides a correctly labeled diagram of the process
Describes the esterification procedure
Explains the purpose of refluxing and/or the water bath
Lists the safety precautions to be taken
Identifies some of the reagents used
Provides a general diagram of the process
Briefly describes the esterification procedure and identifies the need
for refluxing and/or the water bath
Lists the safety precautions to be taken
Marks
6-7
4-5
3
•
•
•
Identifies some of the reagents used
Briefly describes the esterification procedure and includes a diagram
Lists some of the safety precautions to be taken
1-2
Question 28(a)
•
Criteria
Identifies two branches of chemistry, such as physical chemistry,
analytical chemistry, organic chemistry, inorganic chemistry
Marks
1
Question 28(b)
Criteria
• Identifies a specific chemist and their branch of chemistry
• Describes the role/work of this chemist in their occupation
AND
• Relates this to a chemical principle they use
• Identifies a chemist working in a branch of chemistry
AND
• Describes their role
Marks
3
1-2
Question 29(a)
•
•
•
•
Criteria
Accounts for the importance of monitoring heavy metals in
waterways and their impacts on the marine environment
Compares the use of AAS to monitor heavy metal pollution, in
comparison to traditional methods
Identifies the importance of monitoring heavy metals in waterways
Lists the advantages and disadvantages of using AAS
Marks
3
1-2
Question 29(b)
Criteria
• Includes a balanced chemical equation of the Haber process (ie. N2(g)
+ 3H2(g)  2NH3(g))
• Accounts for the needs to monitor different aspects of the reaction
vessel including temperature, pressure, gas ratio, impurities and
contaminants
AND
• Identifies the consequences if monitoring is neglected
• Accounts for the needs to monitor some of the different aspects of the
reaction vessel
OR
• Identifies the consequences if monitoring is neglected
Marks
3
1-2
Question 30(a)
Criteria
Marks
•
Identifies the detrimental effects of CFCs in the stratosphere to the
ozone layer
AND
• Relates this to the effect on humans and/or plants
• Describes how CFCs destroy ozone using a series of relevant
chemical equations
• Identifies the detrimental effects of CFCs in the stratosphere to the
ozone layer
• Describes how CFCs destroy ozone
3
1-2
Question 31(b)
•
•
•
•
Criteria
Identifies the sources of CFCs
Provides a list of the different steps that have been taken to prevent
further release of CFCs, such as the Montreal Protocol, banning of
CFCs and HCFCs, HCF replacements)
Identifies that even after such steps of prevention, it takes a very long
period of time for the ozone to return to its normal state
Briefly describes some steps that have been taken to prevent the
release of CFCs
Marks
2-3
1
Question 35(a)
•
Criteria
Identifies that the molecule is an amino acid
Marks
1
Question 35(b)
Criteria
Correctly identifies a distinguishing test for each carbon
compound
• Correctly identifies the positive result for ALL chemical tests
• Includes at least TWO chemical equations including states
• Identifies at least TWO distinguishing tests
• Correctly identifies the positive test for at least ONEidentified
distinguishing tests
• Includes at least ONE correct chemical equation with incorrect or
without states
OR
• Identifies at least THREE distinguishing tests
• Incorrectly identifies ONE or more positive test
• Includes at least ONE correct chemical equation with incorrect or
without states
Completes at least TWO of the following:
• Identifies at least ONE distinguishing test
OR
• Identifies the positive test of ONE distinguishing test
•
Marks
4
2-3
1
OR
• Includes ONE chemical equation
Question 35(c)
Criteria
Identifies that both glycosidic bond and a peptide bond is
produced by condensation polymerisation
• Identifies that a glycosidic bond is formed by two carbohydrates
while a peptide bond is formed by two amino acids
• Describes the difference between a glycosidic bond and a peptide
bond
• Correctly does any TWO of the above.
• Correctly does any ONE of the above.
•
Marks
3
2
1
Question 35(d)(i)
•
Criteria
Identifies that the technique used is electrophoresis
Marks
1
Question 35(d)(ii)
Criteria
• Identifies that chromatography requires a solute dissolved in the
solvent
• Explains how paper chromatography works with reference to
polarity
• Suggests a possible use of paper chromatography in forensic
chemistry
• Any TWO of the above.
• Any ONE of the above.
Marks
3
2
1
Question 35(e)
Criteria
• Identifies that the DNA structure is a double helix
• Identifies that there are two backbones and refers to deoxyribose
sugar groups, phosphate groups AND nitrogen bases
OR
• Identifies that the DNA structure is a double helix
• Identifies that there are two backbones and refers to nitrogen
bases
• Identifies that the four nitrogen bases form hydrogen bonds
• Identifies any TWO of the above
• Identifies any ONE of the above
Marks
3
2
1
Question 35(f)
•
Criteria
Identifies at least THREE instrumental techniques.
Marks
6-7
• Discusses the value of each instrumental techniques, including at
least TWO advantages and TWO disadvantages of each instrumental
technique. Each discussion must refer to cost and time.
• Suggests a use of each technique in forensic chemistry.
• Includes an evaluative statement in reference to the value of
instrumental techniques in forensic chemistry.
• Coherent response and logical progression of ideas.
• Identifies at least THREE instrumental techniques.
• Discusses the value of each instrumental techniques with at least
ONE advantage and disadvantage of each technique including
reference to either cost and/or time.
• Includes an evaluative statement.
• Identifies at least ONE instrumental technique.
• Discusses the value of each at least ONE instrumental techniques
with at least ONE advantage and disadvantage.
• Attempts to answer the question.
• Identifies ONE instrumental technique.
OR
• Gives ONE advantage and/or disadvantage of an instrumental
technique.
OR
• Includes an evaluative statement.
4-5
2-3
1