Chemistry 2015 HSC exam pack (archive)

Candidates showed strength in these areas:

• preparing an indicator (Q21a)
• plotting points on a graph (Q22a)
• outlining the structure of an electrochemical cell (Q23)
• describing the steps of addition polymerisation and relating the use of polymers to their structures and properties (Q25a and b)
• using the correct number of significant figures and units in a calculation (Q26c).

Candidates need to improve in these areas:

• drawing a line of best fit through plotted points (Q22a)
• writing equations to represent the basic nature of the acetate ion and demonstrating how a strong base affects a buffer solution (Q24a and b)
• drawing full structural formulae showing all bonds, including the O-H bond (Q26a)
• identifying the equivalence point of a titration (Q26b)
• discussing the use of a radioisotope in a non-medical industry (Q27)
• justifying the modifications made to the procedure used to collect barium sulphate precipitate (Q29a)
• clearly relating the given graph to the conditions used in the Haber process (Q30).

Question 31

Candidates showed strength in these areas:

• writing a procedure for the safe making of soap (Q31bi)
• using Le Châtelier’s Principle to account for changes in concentration (Q31ai)
• explaining the emulsifying properties of soap (Q31bii)
• extracting data from a flow chart (Q31ci).

Candidates need to improve in these areas:

• calculating an equilibrium constant by using an ICE table or similar to determine the equilibrium concentrations (Q31aii)
• identifying the raw materials required for the Solvay process and justifying the location of a Solvay plant (Q31cii)
• comparing the chemistry of two methods of producing sodium hydroxide (Q31d).

Question 32

Candidates showed strength in these areas:

• outlining the limitations of using paint to protect ships (Q32ai)
• drawing an electrolytic cell (Q32ci).

Candidates need to improve in these areas:

• describing a valid and reliable procedure that can be used to compare the corrosion rates of iron and a named form of steel (Q32bi)
• identifying two types of steel and relating their percentage composition to their properties (Q32bii)
• identifying the differences in conditions between shallow and deep water and explaining the different rusting processes with equations (Q32d).

Question 33

Candidates showed strength in these areas:

• identifying components of a cell involved in respiration  (Q33ai)
• understanding the function of ATP (Q33aii)
• identifying bonding types and the relationship to protein shape (Q33ci)
• comparing metabolic pathways involved in sprinting and walking (Q33d).

Candidates need to improve in these areas:

• understanding the basic structure of ATP and relating it to biological significance (Q33aii)
• understanding validity and reliability in relation to experimentation (Q33bi)
• recognising the limitations of using models in understanding how enzymes function in living systems (Q33bii)
• relating denaturisation of enzymes to their biological activity (Q33cii).

Question 34

Candidates showed strength in these areas:

• identifying the chemical composition of cosmetics used in an ancient culture and their potential health risks (Q34ai)
• explaining the emitted flame colour of metal ions after undergoing excitation (Q34bii)
• assessing the contribution of the Bohr model to our understanding of the atomic structure with reference to emission spectra (Q34d).

Candidates need to improve in these areas:

• understanding the formation of complex compounds with ligands and their resulting reflected colours (Q34aii)
• understanding the use of the first ionisation energy to show the existence of sub-shell and using Hund’s rule to show the possibility of electron repulsion when two electrons occupy the same orbital (Q34ci).

Question 35

Candidates showed strength in these areas:

• extracting information from DNA profile schematics (Q35ci)
• identifying the composition and  structure of cellulose (Q35ai)
• describing a test for protein in egg white (Q35bii).

Candidates need to improve in these areas:

• assessing the use of a chromatography technique in the analysis of forensic evidence (Q35d)
• describing a valid procedure (Q35bii)
• describing the relationship between amino acids and proteins (Q35bi).