Chemistry 2016 HSC exam pack (archive)

Candidates showed strength in these areas:

• writing half equations for an anode and a cathode (Q21)
• identifying safety issues (Q22)
• writing an equation, with full structural formulae, for the production of an ester (Q22)
• drawing a graph with correct orientation and labelling of axes (Q23a)
• calculating and applying molar masses (Q25)
• identifying that condensation polymerisation produces water (Q26a)
• setting out a calculation in a logical order and using units in each step (Q27)
• identifying equilibrium on a graph (Q28)
• writing a neutralisation equation and determining the mole ratio from the equation (Q29).

Candidates need to improve in these areas:

• completing all parts of the question (Q21a)
• providing the state for species and balancing overall cell equations (Q21b)
• justifying the use of a reflux condenser, for example, in terms of the need for faster reaction, rather than simply describing its use (Q22c)
• using the full grid for the graph and not starting at zero (Q23a)
• using the data provided to calculate the energy released (Q23b)
• using a ruler and a dark pencil, such as a 2B pencil, to construct a good quality diagram (Q24a)
• understanding the process of eutrophication (Q24b)
• linking cause and effect (Q24a and Q24b)
• including correct units in calculation answers (Q25)
• justifying rather than simply outlining or identifying issues (Q26b)
• writing a reversible equation in the direction that shows decomposition (Q28b)
• explaining how an equilibrium system responds to a disturbance by referring specifically to absorbing heat, rather than providing general statements such as ‘favouring the endothermic direction’ (Q28b)
• addressing the question, rather than providing an outline or a rote-learned response (Q30).

Question 31

Candidates showed strength in these areas:

• writing a procedure (Q31bi)
• understanding how changes in temperature and volume alter equilibrium (Q31ci).

Candidates need to improve in these areas:

• writing an acceptable equation for saponification(Q31d)
• using Le Chatelier’s Principle to clearly articulate how and why equilibrium changes (Q31ci)
• knowing the concentration of a solid in an equilibrium calculation (Q31cii).

Question 32

Candidates showed strength in these areas:

• using a chemical equation to describe a process in an electrochemical cell (Q32aii)
• providing examples of passivating metals and sacrificial anodes (Q32c)
• describing some processes that can be used to restore an iron artefact (Q32d).

Candidates need to improve in these areas:

• explaining, by linking the cause and effect, rather than merely describing (Q32bii)
• using chemical equations to support a response when appropriate (Q32d).

Question 33

Candidates showed strength in these areas:

• identifying the bonding in amino acids (Q33a)
• describing the benefits of using models (Q33b)
• calculating the molar mass of glucose (Q33c)
• explaining Type 1 and Type 2 muscles (Q33d).

Candidates need to improve in these areas:

• relating denaturing of an enzyme to an increase in kinetic energy (Q33a)
• relating glycoside bonding between –OH groups to the formation of glycogen (Q33b)
• relating both acetyl-CoA and glycerol formation to the metabolism of fats and their subsequent role in ATP production (Q33c).

Question 34

Candidates showed strength in these areas:

• explaining the production of flame colours (Q34a)
• explaining the need for pigments to be insoluble (Q34c)
• naming or drawing complex ions and stating their colour (Q34d).

Candidates need to improve in these areas:

• understanding infra-red spectroscopy techniques (Q34c)
• recognising that d-d splitting occurs in the metal ion (Q34d).

Question 35

Candidates showed strength in these areas:

• describing methods of collecting evidence that improve accuracy (Q35a)
• identifying metal ions present in a mixture using AES (Q35c).

Candidates need to improve in these areas:

• understanding electrophoresis and the structure of amino acids (Q35b)
• identifying features of DNA (Q35d)
• understanding the difference between Atomic Absorption Spectroscopy and Atomic Emission Spectroscopy (Q35c).