Chemistry marking guide and solution - Queensland Curriculum and ...
Chemistry marking guide and
solution
Sample external assessment 2020
Science (125 marks)
Assessment objectives
This assessment instrument is used to determine student achievement in the following
objectives:
1. describe and explain chemical equilibrium systems, oxidation and reduction, properties and
structure of organic materials, and chemical synthesis and design
2. apply understanding of chemical equilibrium systems, oxidation and reduction, properties
and structure of organic materials, and chemical synthesis and design
3. analysis evidence about chemical equilibrium systems, oxidation and reduction, properties
and structure of organic materials, and chemical synthesis and design to identify trends,
patterns, relationships, limitations or uncertainty
4. interpret evidence about chemical equilibrium systems, oxidation and reduction, properties
and structure of organic materials, and chemical synthesis and design to draw conclusions
based on analysis.
Introduction
The Queensland Curriculum and Assessment Authority (QCAA) has developed mock external
assessments for each General senior syllabus subject to support the introduction of external
assessment in Queensland.
An external assessment marking guide (EAMG) has been created specifically for each mock
external assessment.
The mock external assessments and their marking guides were:
? developed in close consultation with subject matter experts drawn from schools, subject
associations and universities
? aligned to the external assessment conditions and specifications in General senior syllabuses
? developed under secure conditions.
Purpose
This document consists of an EAMG and an annotated response.
The EAMG:
? provides a tool for calibrating external assessment markers to ensure reliability of results
? indicates the correlation, for each question, between mark allocation and qualities at each
level of the mark range
? informs schools and students about how marks are matched to qualities in student responses.
Mark allocation
Where a response does not meet any of the descriptors for a question or a criterion, a mark of ¡®0¡¯
will be recorded.
Where no response to a question has been made, a mark of ¡®N¡¯ will be recorded.
Marking guide and solution
Sample external assessment 2020
Queensland Curriculum & Assessment Authority
External assessment marking guide
Paper 1 ¡ª Section 1: Multiple choice
Question
Response
1
C
2
D
3
B
4
A
5
B
6
A
7
B
8
D
9
C
10
C
11
D
12
A
13
C
14
D
15
B
16
A
17
D
18
D
19
C
20
D
21
B
22
D
23
C
24
A
25
D
Chemistry marking guide and solution
Sample external assessment 2020
Queensland Curriculum & Assessment Authority
Paper 1 ¡ª Section 2: Short response
Question
Sample response
The response
26
a)
D
? determines structure with
tertiary carbon is D [1 mark]
b)
propan-2-ol
? determines name is
propan-2-ol [1 mark]
Ethane is insoluble in water because it contains only a non-polar
hydrocarbon chain. The inter-molecular forces are dispersion forces
only.
? identifies that ethane is
insoluble due to dispersion
forces [1 mark]
Ethanol and ethanoic acid are both soluble in water as the hydroxyl (ROH) and carboxyl (R-COOH) groups forms H-bonds with water
molecules
? identifies that ethanol is
soluble due to H-bonds
between the hydroxyl group
and water [1 mark]
The non-polar hydrocarbon chains in ethanol and ethanoic acid are
small and have weak dispersion forces which do not interfere with the
H-bonding and their solubility in water.
? identifies that ethanoic acid is
soluble due to H-bonding
between the carboxyl group
and water [1 mark]
27
Chemistry marking guide and solution
Sample external assessment 2020
Queensland Curriculum & Assessment Authority
Question
Sample response
28
29
The response
? correctly identifies
equivalence point > 7
[1 mark]
? correctly identifies buffer
region [1 mark]
? identifies initial pH 3 [1 mark]
a)
b)
Stage 2
? identifies stage 2 [1 mark]
Because it¡¯s a reversible reaction where all the products and reactants
are gases.
? indicates stage 2 is affected
by pressure because it is
reversible, and all of the
reactants and products are
gases [1 mark]
??H2 SO4 required = 1 100 000/98.08 = 11 215 mol
? correctly determines
??H2 SO4 = 11 215 [1 mark]
??SO3 required = 11 215/0.97 = 11 562 mol
??SO3 : ??S = 1:1 = 11 562 mol
mass S = 11 562 ¡Á 32.06 = 370 678 g
Mass = 371 kg
Chemistry marking guide and solution
Sample external assessment 2020
? determines ??SO3 = 11 562
[1 mark]
? determines ??SO3 : ??S = 11 562
[1 mark]
? determines mass S = 371
[1 mark]
Queensland Curriculum & Assessment Authority
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