STAGE 2 CHEMISTRY
ASSESSMENT TYPE 1: Investigations Folio
Practical Investigation: Preparation of an Ester
Response 1
Skills checklist (Teacher record)
Part A:
Teacher observations:
Performing reflux
Clamped correctly. Vapours reached the top of the
condenser.
Use of separating funnel
Careful.
Performing distillation
Clamped correctly. Adaptor joint under strain.
Thermometer too low.
Clarity of ester product
Cloudy.
Area cleanliness
Clean and well-organised.
Safe conduct
Good – aware of closeness of other groups. All
precautions observed.
Investigation
Manipulates
apparatus
generally
carefully and
effectively to
implement safe
and ethical
investigation
procedures.
Disposed of excess chemicals and prepared ester down
the sink.
Cooperation
Generally good communication between partners.
Other
Had to be told to tie hair back.
Application
Applies mostly
constructive and
focused
individual and
collaborative
work skills.
Student Report
Application
Formulae,
equations,
chemical terms
all correct.
Effective use of
formulae,
equations,
chemical terms.
Correct name of
product.
Results
Distillation range: 128 - 135C
Ester has a sweet odour.
Discussion
Reaction equation:
CH3COOH + CH3CH2CH2CH2CH2-OH
CH3COO CH2CH2CH2CH2CH3
+ H2O
pentyl ethanoate
Reflux procedure
The reactants must be heated for an extended period. This is a problem because the
liquids are volatile and so will evaporate and this will mean that not much product will
form. Safety will also be a problem. By heating under reflux conditions the vapours
condense on the sides of the water-cooled condenser so that the liquids fall back into the
pear-shaped flask so that no reactants or products are lost during the heating process.
Page 1 of 5
Stage 2 Chemistry annotated response
Ref: A107234 (revised January 2013)
© SACE Board of South Australia 2013
Isolation procedures
1. Initial washing with water
At the end of the heating period all reactants and products are present in the mixture.
This is because the system reaches a state of chemical equilibrium and the
concentrations of all species remain unchanged. Washing with water will remove most
of the water-soluble substances.
The aqueous layer was identified by adding some distilled water and seeing which
layer increased in volume. This layer was removed and the ester layer left in the
separating funnel.
2. Washing with Na2CO3 solution
After the washing with water there will still be traces of acid left in the ester layer.
These can be removed by reaction with Na2CO3.
2H+ + CO32-  CO2 + H2O
Analysis and
Evaluation
Logically
evaluates
procedures.
Demonstrates
understanding of
chemical
principles behind
practical
procedures.
Some appropriate
improvements.
3. Final washing with water
This removes any traces of water-soluble materials (such as the salts formed in the last
washing) from the separating funnel.
4. Stand over CaCl2
CaCl2 is a dehydrating agent and so removes any traces of water trapped in the ester
layer. There was so much water that it formed a new layer.
5. Distillation
Distillation allows the separation of liquids that have different boiling points as each
liquid has its own boiling point and the temperature only rises when that liquid has been
completely boiled off. The ester had the highest boiling point and so was collected last.
Poor Yield
This method results in a poor yield of ester because:

the reaction was not refluxed for long enough

the reaction reaches an equilibrium so that 100% product yield cannot be obtained
– the concentrations of all species, reactants and products, will remain constant

a little bit of ester is lost at every washing – some is let through the tap of the
separating funnel, with the aqueous layer.
Page 2 of 5
Stage 2 Chemistry annotated response
Ref: A107234 (revised January 2013)
© SACE Board of South Australia 2013
Modifications to improve yield of ester
1. Reflux the reaction mixture for longer so that more reactants are converted into
products.
2. An increased concentration of one of the reactants (eg, the acid) could be used to
push the equilibrium to the right and so improve the yield of ester.
3. The separating funnel could be used more carefully so that less ester gets through
with the aqueous layers.
Modifications to improve purity of ester
The preparation could be carried out more carefully to get a better boiling point and a
clearer ester.
Safety hazards/precautions
1. Safety glasses, and plastic apron were worn and any heating was done with a tiny
flame and constant observation.
2. When the mixture was shaken with Na2CO3 solution a gas (CO2) formed in the
separating funnel and could have caused the tap or stopper to burst out and spill
the liquids. The tap of the funnel was opened often to allow the gas to escape
before it built up badly. When the tap was opened it was turned away from people
so that no liquids got onto their faces.
Review of team-work
This preparation would have been difficult to undertake individually as two pairs of hands
were definitely an advantage in setting up for the reflux and the distillation. In the formative
prac we had discussed ways in which to work most efficiently (eg one partner to handle the
glassware and the other to be responsible for the clamps when setting up the distillation)
and had come into the lab one lunch time to practice.
We shared the heating during the reflux and distillation. We each heated for about 10
minutes whilst the other partner made and recorded observations, kept the bench
uncluttered and got organized for the next part of the prac. Both of us tend to work neatly
and to clean up as we go so we worked really well together.
We were both disappointed at getting a cloudy ester. It was a pity we didn’t have more
time so that we could have done a second distillation as this would probably have resulted
in a better quality ester.
Additional Comments
More than one assessment will need to be considered to assess ability to:
 use appropriate chemical terms, conventions, formulae and equations highly effectively (A grade descriptor)
 communicate knowledge and understanding highly effectively in different formats (A grade descriptor).
Knowledge and Understanding
Knowledge and understanding communicated coherently and highly effectively in an appropriate report format.
Page 3 of 5
Stage 2 Chemistry annotated response
Ref: A107234 (revised January 2013)
© SACE Board of South Australia 2013
Performance Standards for Stage 2 Chemistry – Practical Investigation: Preparation of an
Ester
A
Investigation
Analysis and Evaluation
Application
Knowledge and
Understanding
Designs logical, coherent, and
detailed chemistry investigations.
Critically and systematically
analyses data and their
connections with concepts, to
formulate logical and perceptive
conclusions and make relevant
predictions.
Applies chemistry concepts and
evidence from investigations to
suggest solutions to complex
problems in new and familiar
contexts.
Consistently demonstrates a deep
and broad knowledge and
understanding of a range of
chemistry concepts.
Critically and logically selects and
consistently and appropriately
acknowledges information about
chemistry and issues in chemistry
from a range of sources.
Manipulates apparatus and
technological tools carefully and
highly effectively to implement
well-organised safe and ethical
investigation procedures.
Uses appropriate chemical terms,
conventions, formulae, and
equations highly effectively.
Uses knowledge of chemistry
perceptively and logically to
understand and explain social or
environmental issues.
Demonstrates initiative in applying
constructive and focused
individual and collaborative work
skills.
Uses a variety of formats to
communicate knowledge and
understanding of chemistry
coherently and highly effectively.
Applies chemistry concepts and
evidence from investigations to
suggest solutions to problems in
new and familiar contexts.
Demonstrates some depth and
breadth of knowledge and
understanding of a range of
chemistry concepts.
Uses appropriate chemical terms,
conventions, formulae, and
equations effectively.
Uses knowledge of chemistry
logically to understand and explain
social or environmental issues.
Applies mostly constructive and
focused individual and
collaborative work skills.
Uses a variety of formats to
communicate knowledge and
understanding of chemistry
coherently and effectively.
Analyses data and their
connections with concepts, to
formulate generally appropriate
conclusions and make simple
predictions, with some relevance.
Applies chemistry concepts and
evidence from investigations to
suggest some solutions to basic
problems in new or familiar
contexts.
Demonstrates knowledge and
understanding of a general range of
chemistry concepts.
Evaluates some procedures in
chemistry and suggests some
improvements that are generally
appropriate.
Uses generally appropriate
chemical terms, conventions,
formulae, and equations with
some general effectiveness.
Critically and logically evaluates
procedures and suggests a range
of appropriate improvements.
Obtains, records, and displays
findings of investigations using
appropriate conventions and
formats accurately and highly
effectively.
B
Designs well-considered and clear
chemistry investigations.
Logically selects and appropriately
acknowledges information about
chemistry and issues in chemistry
from different sources.
Manipulates apparatus and
technological tools carefully and
mostly effectively to implement
organised safe and ethical
investigation procedures.
Clearly and logically analyses
data and their connections with
concepts, to formulate consistent
conclusions and make mostly
relevant predictions.
Logically evaluates procedures
and suggests some appropriate
improvements.
Obtains, records, and displays
findings of investigations using
appropriate conventions and
formats mostly accurately and
effectively.
C
Designs considered and generally
clear chemistry investigations.
Selects with some focus, and
mostly appropriately
acknowledges, information about
chemistry and issues in chemistry
from different sources.
Manipulates apparatus and
technological tools generally
carefully and effectively to
implement safe and ethical
investigation procedures.
Applies generally constructive
individual and collaborative work
skills.
Uses knowledge of chemistry with
some logic to understand and
explain one or more social or
environmental issues.
Uses different formats to
communicate knowledge and
understanding of chemistry with
some general effectiveness.
Obtains, records, and displays
findings of investigations using
generally appropriate conventions
and formats with some errors but
generally accurately and
effectively.
Page 4 of 5
Stage 2 Chemistry annotated response
Ref: A107234 (revised January 2013)
© SACE Board of South Australia 2013
D
Investigation
Analysis and Evaluation
Application
Knowledge and
Understanding
Prepares the outline of one or
more chemistry investigations.
Describes basic connections
between some data and
concepts, and attempts to
formulate a conclusion and make
a simple prediction that may be
relevant.
Applies some evidence to
describe some basic problems
and identify one or more simple
solutions, in familiar contexts.
Demonstrates some basic
knowledge and partial
understanding of chemistry
concepts.
Attempts to use some chemical
terms, conventions, formulae, and
equations that may be
appropriate.
Identifies and explains some
chemistry information that is
relevant to one or more social or
environmental issues.
Attempts individual work
inconsistently, and contributes
superficially to aspects of
collaborative work.
Communicates basic information to
others using one or more formats.
Attempts to connect data with
concepts, formulate a conclusion,
and make a prediction.
Identifies a basic problem and
attempts to identify a solution in a
familiar context.
Demonstrates some limited
recognition and awareness of
chemistry concepts.
Acknowledges the need for
improvements in one or more
procedures.
Identifies some chemical terms or
formulae.
Shows an emerging understanding
that some chemistry information is
relevant to social or environmental
issues.
Selects and may partly
acknowledge one or more sources
of information about chemistry or
an issue in chemistry.
Uses apparatus and technological
tools with inconsistent care and
effectiveness and attempts to
implement safe and ethical
investigation procedures.
For some procedures, identifies
improvements that may be made.
Obtains, records, and displays
findings of investigations using
conventions and formats
inconsistently, with occasional
accuracy and effectiveness.
E
Identifies a simple procedure for a
chemistry investigation.
Identifies a source of information
about chemistry or an issue in
chemistry.
Attempts to use apparatus and
technological tools with limited
effectiveness or attention to safe
or ethical investigation procedures.
Shows emerging skills in
individual and collaborative work.
Attempts to communicate
information about chemistry.
Attempts to record and display
some descriptive information about
an investigation, with limited
accuracy or effectiveness.
Page 5 of 5
Stage 2 Chemistry annotated response
Ref: A107234 (revised January 2013)
© SACE Board of South Australia 2013