QCAA Chemistry Paper 2 2023 PDF

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LUI School code School name Given name/s Attach your barcode ID label here Family name Book of books used External assessment 2023 Question and response book Chemistry Paper 2 Time allowed Section 1 (54 marks) Clear zone — margin trimmed off after completion of assessment Perusal time — 10 minutes 9 short response questions Working time — 90 minutes General instructions Answer all questions in this question and response book. Write using black or blue pen. QCAA-approved calculator permitted. QCAA formula and data book provided. Planning paper will not be marked.  DO NOT WRITE ON THIS PAGE THIS PAGE WILL NOT BE MARKED  Section 1 Instructions If you need more space for a response, use the additional pages at the back of this book. – On the additional pages, write the question number you are responding to. – Cancel any incorrect response by ruling a single diagonal line through your work. – Write the page number of your alternative/additional response, i.e. See page … – If you do not do this, your original response will be marked. DO NOT WRITE ON THIS PAGE THIS PAGE WILL NOT BE MARKED Do not write outside this box. 1 of 17  QUESTION 1 (2 marks) Polylactic acid (PLA) and low-density polyethylene (LDPE) are both used to produce plastic wrapping film. Plastic Composition Density Tensile stress Elongation (%) Degradation rate (g/cm3) (MPa) PLA plant-based 1.24 60 6 slow LDPE petrochemical-based 0.92 12 148 none Analyse the data to discuss one advantage and one disadvantage of using PLA rather than LDPE to produce plastic wrapping film. Advantage: Disadvantage: Do not write outside this box. 2 of 17  QUESTION 2 (3 marks) Compare the structure of α-helix and β-pleated sheets in the secondary structure of proteins. Similarity: Difference: Significance: Do not write outside this box. 3 of 17  QUESTION 3 (7 marks) An experiment was conducted at standard state conditions to investigate the potential difference (V) produced by different galvanic cells. The three cells used in the experiment are shown. V Ag(s) Salt bridge graphite Cell 1 AgNO3 Cu(NO3)2 V Mg(s) Salt bridge graphite Cell 2 Mg(NO3)2 Cu(NO3)2 V Cu(s) Salt bridge graphite Cell 3 Cu(NO3)2 AgNO3 Do not write outside this box. 4 of 17  (a) Predict which cell produced the highest voltage. Explain your reasoning. [3 marks] (b) Determine the maximum voltage that could be produced by a fourth galvanic cell constructed from any of the components used in the first three cells. Use oxidation and reduction half-equations to justify your answer. [4 marks] Do not write outside this box. 5 of 17  QUESTION 4 (8 marks) Compound C has the molecular formula C4H10O and is either an alcohol, an aldehyde or a carboxylic acid. Compound C infrared spectrum 0.8 Transmittance 0.6 0.4 0.2 3000 2000 1000 Wavenumber (cm–1) (a) Deduce the class of compound C. Explain your reasoning. [4 marks] Do not write outside this box. 6 of 17  (b) Deduce the structural formula and IUPAC name of two isomers of compound C. [2 marks] Isomer 1: IUPAC name:  Isomer 2: IUPAC name:  Note: If you make a mistake in the drawing, cancel it by ruling a single diagonal line through your work and use the additional response space at the back of this question and response book. (c) Distinguish between structural and geometric isomers. [2 marks] Do not write outside this box. 7 of 17  QUESTION 5 (13 marks) The table gives the properties of four monoprotic acids. Acid Concentration (mol L-1) [H +] (mol L-1) pH Ka 1 0.200 7.90 × 10-5 2 0.100 4.20 × 10-3 2.34 1.80 × 10-4 CH3COOH(aq) 0.100 1.78 × 10-5 HCl(aq) 0.010 1.00 × 10-2 2.00 >1 (a) Determine the relative strength of acids 1 and 2 by contrasting their Ka values. [3 marks] (b) Write a balanced chemical equation for the dissociation of ethanoic acid (CH3COOH) in water.  [2 marks] (c) Identify whether the conjugate base of ethanoic acid (CH3COOH(aq)) is amphiprotic. Explain your reasoning. [2 marks] Do not write outside this box. 8 of 17  (d) Calculate the pH of the aqueous solution of ethanoic acid (CH3COOH). Show your working. [3 marks] (e) Determine the volume of water that would need to be added to 100.0 mL of HCl(aq) to change the pH from 2.00 to 3.00. Explain your reasoning. [3 marks] Do not write outside this box. 9 of 17  QUESTION 6 (6 marks) The reaction shows the base hydrolysis (saponification) of a triglyceride to produce glycerol and a soap. O CH2 O C (CH2)14 CH3 CH2 OH O O CH O C (CH2)14 CH3 + 3NaOH CH OH + 3H3C (CH2)14 C ONa O CH2 O C (CH2)14 CH3 CH2 OH Triglyceride Glycerol Soap (a) Identify which compound in the reaction is an ester. [1 mark] (b) Contrast the structure of saturated and unsaturated fatty acids. [1 mark] Do not write outside this box. 10 of 17  (c) Explain how the cleaning action of soap is related to its structure. [4 marks] Do not write outside this box. 11 of 17  QUESTION 7 (4 marks) When heated in a sealed container, solid mercury(II) oxide (HgO) decomposed to form metallic mercury (Hg) and oxygen gas (O2). 2HgO(s)  2Hg(l) + O2(g) Orange Silver Colourless (a) Identify whether the reaction occurs in an open or closed system. [1 mark] (b) Explain why the colour of the system does not change once equilibrium is established. [3 marks] Do not write outside this box. 12 of 17  QUESTION 8 (7 marks) Two experiments were conducted to investigate the effect of temperature on the equilibrium formed during the decomposition of hydrogen iodide (HI). 2HI(g)  H2(g) + I2(g) ∆H = + 53.6 kJ mol-1 Initial concentration Equilibrium concentration Experiment (mol L-1) (mol L-1) Kc [HI] [H2] [I2] [HI] [H2] [I2] 1 0.08 0.00 0.00 0.01 2.78 × 10−2 2 0.00 0.06 0.06 0.06 0.03 0.03 (a) Determine the concentration of HI(g) and I2(g) at equilibrium for experiment 1. [2 marks] [HI]: [I2]: (b) Calculate the equilibrium constant (Kc) for experiment 2. Show your working. [2 marks] (c) Determine which experiment was conducted at a higher temperature. Explain your reasoning. [3 marks] Do not write outside this box. 13 of 17  QUESTION 9 (4 marks) Aspirin (C9H8O4) can be produced from a reaction between salicylic acid (C7H6O3) and acetic anhydride (C4H6O3) with ethanoic acid being a minor product. C7H6O3(s) + C4H6O3(aq) → C9H8O4(s) + C2H4O2(aq) Calculate the mass of salicylic acid required to produce 8.25 g of aspirin if the percentage yield of the reaction is 60%. Show your working. END OF PAPER Do not write outside this box. 14 of 17  ADDITIONAL PAGE FOR STUDENT RESPONSES Write the question number you are responding to. Do not write outside this box. 15 of 17  ADDITIONAL PAGE FOR STUDENT RESPONSES Write the question number you are responding to. Do not write outside this box. 16 of 17  ADDITIONAL PAGE FOR STUDENT RESPONSES Write the question number you are responding to. Do not write outside this box. 17 of 17 Back cover References Question 4 Minor adaptation from Coblentz Society, Inc., 2-Butanol 2018, in NIST Chemistry WebBook, NIST Standard Reference Database Number 69, Nist.gov, National Institute of Standards and Technology, U.S. Secretary of Commerce https://webbook.nist.gov/cgi/cbook.cgi?ID=C78922&Type=IR- SPEC&Index=1 Clear zone — margin trimmed off after completion of assessment © State of Queensland (QCAA) 2023 Licence: https://creativecommons.org/licenses/by/4.0 | Copyright notice: www.qcaa.qld.edu.au/copyright — lists the full terms and conditions, which specify certain exceptions to the licence. | Attribution: © State of Queensland (QCAA) 2023