Year 12 Chemistry Topics and Practice Questions 2022.pdf

Chemistry Units 3 and 4 Practice Questions Use the checklists for each topic to help you focus on the skills and concepts you need to practice. This booklet provides some practice questions. Use your textbook, worksheets and lessons covered through the year as well. Steps to use practice questions...

Chemistry Units 3 and 4 Practice Questions Use the checklists for each topic to help you focus on the skills and concepts you need to practice. This booklet provides some practice questions. Use your textbook, worksheets and lessons covered through the year as well. Steps to use practice questions 1. Select a topic that you will focus on for that session. Sessions should last 20-30 minutes. 2. Review your notes and actively summarise by writing dot points, creating mind maps or other visuals such as flow charts or flash cards. If you are an auditory learner, read these out loud or tell another person. 3. Close your notes. 4. Complete practice questions from that topic without referring to your notes (use as many sources as possible for these questions) 5. Mark your question responses and identify areas that you did well in and areas that could improve. 6. Review your notes about the areas that you need to improve and schedule review of this topic in 1-2 weeks to repeat. 7. Next time you review a topic, start by doing questions without looking at notes, mark your work and then actively make notes. 8. Develop a plan to cover all topics multiple times over the year. 9. Alternate whether you start with note taking or questions for each of your study sessions on topics. Other Revision Techniques Use the Feynman technique – in this technique you explain a topic in simple terms, as if you were teaching a child. Identify gaps in your explanation that you couldn’t explain simply. Go back to your notes and review those areas until you can explain it simply. See this video for an explanation - https://www.youtube.com/watch?v=q-16DPh_VWw Contents Unit 3....................................................................................................................................................... 3 Chemical Equilibrium.......................................................................................................................... 3 Acids and Bases................................................................................................................................... 9 Redox Reactions................................................................................................................................ 15 Electrochemical cells......................................................................................................................... 17 Unit 3 Multiple Topics........................................................................................................................... 22 Unit 4..................................................................................................................................................... 23 Structure of organic compounds...................................................................................................... 23 Physical properties and trends......................................................................................................... 26 Organic reactions and reaction pathways........................................................................................ 29 Organic materials: structure and function........................................................................................ 35 Analytical techniques........................................................................................................................ 38 Chemical synthesis............................................................................................................................ 41 Green chemistry................................................................................................................................ 44 Macromolecules: polymers, proteins and carbohydrates................................................................ 46 Molecular manufacturing................................................................................................................. 48 Unit 4 Multiple Topics........................................................................................................................... 50 Units 3 and 4 Multiple Topics............................................................................................................... 51 References............................................................................................................................................ 52 2 Unit 3 Chemical Equilibrium o Identify the position of equilibrium from graphical data o Explain the reversibility of reactions by considering the forward and reverse activation energies o Explain and predict the effect of temperature changes utilising changes in enthalpy (exo vs endo) o Apply Le Chatelier’s principle to explain and predict the effect of changes in concentration, pressure, temperature and addition of a catalyst on the position of equilibrium and the equilibrium constant o Deduce equilibrium law expressions for homogeneous reactions o Deduce the extent of a reaction from the magnitude of the equilibrium constant o Use the value of Kc to predict relative amounts of reactants and products at equilibrium o Solve problems related to equilibrium including calculating Kc and concentrations of reactants and products 3 1. In an open chemical system A. energy but not matter is exchanged with the surrounds. B. matter but not energy is exchanged with the surrounds. C. both matter and energy are exchanged with the surrounds. D. neither energy nor matter is exchanged with the surrounds. 2. Methanol can be produced from the reaction of carbon monoxide and hydrogen, according to the following equation: Which set of conditions will produce the maximum yield of methanol? A. Low pressure and low temperature B. Low pressure and high temperature C. High pressure and low temperature D. High pressure and high temperature 3. Predict the effect that increasing temperature will have on the following reaction. N2(g) + O2(g) ⇌ 2NO(g) ΔH = +181 kJ mol–1 A. The equilibrium position will not change. B. The equilibrium position will move towards the reactants (left). C. The equilibrium position will move towards the products (right). D. It is impossible to predict the effect on the equilibrium position. 4. Deduce the correct equilibrium law expression for the following reaction. H2(g) + I2(g) ⇌ 2HI(g) 5. The four equations below represent different equilibrium systems. Equation 1 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH = –180 kJ mol–1 Equation 2 CO(g) + H2O(g) ⇌ CO2(g) + H2(g) ΔH = –46 kJ mol–1 Equation 3 PCl5(g) ⇌ PCl3(g) + Cl2(g) ΔH = 93 kJ mol–1 Equation 4 CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) ΔH = 205 kJ mol–1 After equilibrium was established in each system, the temperature was decreased and the pressure was increased. In which equilibrium system would both changes result in an increase in yield? A. Equation 1 B. Equation 2 C. Equation 3 D. Equation 4 4 6. At equilibrium, a 1.00 L vessel contains 0.0430 mol of H2, 0.0620 mol of I2, and 0.358 mol of HI. The system is represented by the following equation: H2(g) + I2(g) ⇌ 2HI(g) Which of the following is closest to the value of the equilibrium constant, Kc, for this reaction? A. 0.0208 B. 48.1 C. 134 D. 269 7. Nitrogen dioxide, NO2(g), is formed when nitrogen monoxide, NO(g), undergoes oxidation as shown below. 2 NO(g) + O2(g) ⇌ 2 NO2(g) ΔH = − 62 kJ mol-1 A change was imposed on an equilibrium gas mixture of NO2, NO and O2. The mixture returned to equilibrium and another change was imposed. The following graph shows the effects of the two changes. Identify the imposed changes that best account for the shape of the graph. 5 8. A student is investigating the following reaction system. 2NO2(g) ⇌ N2O4(g) ΔH < 0 brown colourless a) The reaction system can be observed in a sealed test tube, which allows the student to investigate the impact of temperature on the equilibrium position of the reaction. State the colour change expected when the student places the sealed test tube of the gas mixture in a beaker of hot water. Explain why this colour change occurs. b) Below is the concentration versus time graph for the reaction system. The graph was produced using secondary data at a temperature of 22 °C. i. Time t1 is shown on the graph above. Calculate the equilibrium constant at time t1. ii. At time t2 the volume of the system was halved, keeping the temperature at 22 °C. Continue the graph to show how this change would affect the reaction system and how the system would respond to this change until equilibrium is restored. 6 9. The concentrations of reactants and products as a function of time for the following system were determined. CO(g) + H2O(g) ⇌ CO2(g) + H2(g) At time T, some CO(g) was removed from the system. a) The concentration of CO after time T is shown. Sketch the concentrations after time T for the remaining species. b) Using Le Chatelier’s Principle, explain the change in the concentration of CO after time T. 10. The following reaction occurs in an aqueous solution. HgCl42-(aq) + Cu2+(aq) ⇌ CuCl42-(aq) + Hg2+(aq) Kc = 4.55 × 10−11 A solution containing a mixture of HgCl42-(aq) and Cu2+(aq) ions is prepared. The initial concentration of each ion is 0.100 mol L–1 and there are no other ions present. Calculate the concentration of Hg2+(aq) ions once the system has reached equilibrium. 7 11. The reaction between nitrogen gas (N2) and oxygen gas (O2) to produce nitrogen monoxide (NO) is given by the following equation. N2(g) + O2(g) ⇌ 2NO(g) ΔH = +181 kJ mol–1 When nitrogen gas and oxygen gas are mixed in a closed 1.00 L container, the concentration of each species can be measured at regular intervals. The graph below shows how the concentration of each species changes over time. a) Identify the number of times that the system establishes equilibrium between t0 and t7. b) Explain what effect a decrease in pressure at time t7 would have on the position of equilibrium. Show your reasoning. c) Predict the effect that an increase in temperature at time t7 would have on the position of the equilibrium and the value of the equilibrium constant (Kc). Show your reasoning. d) Calculate Kc for the above reaction when equilibrium is first established. Show your working. 12. Consider the following equilibrium reaction, which is endothermic. [Co(H2O)6]2+ + 4Cl– ⇌ [CoCl4]2– + 6H2O(l) Pink solution Blue solution Justify TWO conditions that could change the colour of the solution from pink to blue. 13. 0.20 moles of hydrogen gas and 0.20 moles of iodine gas were placed in a 1.0 L container and allowed to come to equilibrium. H(g) + I(g) ⇌ 2HI(g) Determine the equilibrium concentration of HI for this reaction, given that the equilibrium constant, Kc, is 64. 8 Acids and Bases o Define acids as proton donors o Classify monoprotic and diprotic acids o Recognise nitric, hydrochloric and sulfuric as strong acids and carboxylic and carbonic as weak acids o Recognise group 1 and barium hydroxides as strong bases and ammonia and amines as weak bases o Distinguish between strong and weak acids and bases in terms of dissociation, electrical conductivity and reaction with water o Distinguish between the terms strong and concentrated o Use Kw to calculate [H+] from [OH-] o Solve problems for [H+], [OH-], pH and pOH o Represent acid base relationships at equilibrium as chemical equations with acid-base conjugate pairs o Recognise amphiprotic species that act as both acid and base o Identify and deduce the formula or any conjugate acid or base of any Bronsted-Lowry base or acid o Use Le Chatelier’s principle to predict how a buffer solution will respond to the addition of an H+ or OH- o Recognise that the strength of acids is explained by the degree of ionisation at equilibrium in aqueous solution which can be represented by an equilibrium constant Ka o Determine expressions for Ka and Kb for weak acids and bases o Determine and compare the relative strengths of acids and bases from experimental data o Solve problems for Ka, Kb and concentration of reactants and products (where Ka is very small assume [reactants]initial = [reactants]equilibrium and state assumption) o Explain the relationship between the pH range of an acid-base indicator and its pKa value o Identify an appropriate indicator for a titration, given equivalence point of the titration and pH range of the indicator (colour change occurs when pH = pKa, and can be considered to take place over a range of pKa ± 1 o Distinguish between end point and equivalence point o Recognise that titrations rely on identifying equivalence point o Sketch pH against volume (titration curve) graphs involving strong and weak acids and bases o Identify and explain titration curve features – intercept with pH axis, equivalence point, buffer region and points where pKa=pH or pKb=pOH o Solve problems and make predictions from volumetric analysis data to calculate moles, mass, volume and concentration 9 14. HCl(aq) + H2O(l) ⇌ H3O+(aq) + Cl–(aq) The equation above shows A. the transfer of hydrogen ions between conjugate acid-base pairs. B. the transfer of electrons between conjugate acid-base pairs. C. the neutralisation of an acid to produce a conjugate base. D. the neutralisation of an amphoteric species in solution. 15. Which of the following acids can be classified as monoprotic? A. H3PO4 B. H2CO3 C. H2C2O4 D. CH3COOH 16. Determine the pH of a 0.15 M solution of hydrochloric acid (HCl). A. 0.15 B. 0.71 C. 0.82 D. 1.41 17. What is the concentration of hydroxide ions (in mol L–1) in a solution that has a pH of 8.53? A. 3.0 ×10–9 B. 3.4 ×10–6 C. 5.5 D. 3.0 × 105 18. The graph below shows the pH changes during the titration of 10.0 cm3 of a weak base with 0.10 mol dm–3 HCl. The initial concentration of OH– ions in the weak base is A. 10.5 mol dm–3 B. 3.5 mol dm–3 C. 10–3.5 mol dm–3 D. 10–10.5 mol dm–3 10 19. The table below shows the Ka value for several weak acids. Which acid dissociates to form the strongest conjugate base at equilibrium in an aqueous solution? A. acetic acid B. chlorous acid C. nitrous acid D. phosphoric acid 20. Which diagram represents ionisation of a weak acid? 21. A clear, colourless liquid extract of the rhubarb plant was analysed for the concentration of oxalic acid, H2C2O4, by direct titration with a recently standardised and acidified potassium permanganate solution, KMnO4(aq). The balanced equation for this titration is shown below. 2MnO4–(aq) + 5C2O42–(aq) + 16H+(aq) → 2Mn2+(aq) + 10CO2(g) + 8H2O(l) purple colourless colourless The steps in the titration were as follows: Step 1 – A 20.00 mL aliquot of the rhubarb extract was placed in a 200 mL conical flask. Step 2 – The burette was filled with acidified 0.0200 M KMnO4 solution. Step 3 – The acidified 0.0200 M KMnO4 solution was titrated into the rhubarb extract in the conical flask. The titration was considered to have reached the end point when the solution in the conical flask showed a permanent change in colour to pink. The volume of the titre was recorded. Step 4 – The titration was repeated until three concordant results were obtained. The average of the concordant titres was 21.7 mL. The concentration of H2C2O4 in the rhubarb extract is closest to A. 5.43 × 10–2 M B. 5.00 × 10–2 M C. 2.17 × 10–2 M D. 7.40 × 10–4 M 11 22. The diagram represents the titration curve for a reaction between a particular acid and a particular base. Use the diagram to answer Questions 21 and 22. Which indicator would be best for this titration? Indicator Colour change range (pH) Martius yellow 2.0 – 3.2 A. B. Magdala red 3.0 – 4.0 C. Isopicramic acid 4.0 – 5.6 D. Cresol red 7.2 – 8.8 23. Which of the following equations best represents the reaction described by the titration curve? A. NH3(aq) + HCl(aq) NH4Cl(aq) B. NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) C. NH3(aq) + CH3COOH(aq) CH3COONH4(aq) D. NaOH(aq) + CH3COOH(aq) CH3COONa(aq) + H2O(l) 24. Boric acid, which is a weak acid, was titrated with standardised sodium hydroxide solution. Which one of the indicators listed below would be the most suitable to use in this titration? 25. Calculate the concentration of hydroxide ions (OH–) at pH 12.3. Show your working. 12 26. If 15.55 mL of a 0.10 M standardised solution of sodium hydroxide (NaOH) is required to neutralise 10.00 mL of sulfuric acid (H2SO4), calculate the concentration of the sulfuric acid solution (in mol/L). Show your working. 27. A buffer was prepared with acetic acid and sodium acetate. A few drops of universal indicator were then added. When small amounts of either 0.1 mol L–1 HCl(aq) or 0.1 mol L–1 NaOH(aq) were added, no change in the colour of the solution was observed. Explain these observations. Support your answer with at least ONE chemical equation. 28. On the axes below, sketch the titration curve when 0.1 M ethanoic acid (CH3COOH) is titrated with 0.1 M sodium hydroxide (NaOH) and circle the: initial pH of the acid equivalence point buffer region. 13 29. The experiment shown below was set up to investigate the relative strengths of acids. The power supply was connected to two graphite rods. The brightness of the bulb and the electrical conductance for each acid are recorded in the table below. a) Analyse the experimental data to determine which acid is strongest. b) Explain the relationship between the brightness of the bulb, conductivity and the strength of the acids. 30. The relationship between the acid dissociation constant, Ka, and the corresponding conjugate base dissociation constant, Kb, is given by: Ka × Kb = Kw Assume that the temperature for part (a) and part (b) is 25°C. (a) The Ka of hypochlorous acid (HOCl) is 3.0 × 10−8. Show that the Kb of the hypochlorite ion, OCl–, is 3.3 × 10−7. (b) The conjugate base dissociation constant, Kb, is the equilibrium constant for the following equation: OCl–(aq) + H2O(l) ⇌ HOCl(aq) + OH–(aq) Calculate the pH of a 0.20 mol L−1 solution of sodium hypochlorite (NaOCl). 31. A student adds 1.17 g of Al(OH)3(s) to 0.500 L of 0.100 mol L–1 HCl(aq). Calculate the pH of the resulting solution. Assume that the volume of the resulting solution is 0.500L. 14 Redox Reactions o Recognise that a variety of reactions including displacement reactions of metals, combustion, corrosion and electrochemical processes can be modelled as redox reactions involving oxidation and reduction o Predict and explain the ability of an atom to gain or lose electrons based on its position in the periodic table, valence electrons, energy and overall stability of the atom o Identify the species oxidised and reduced o Deduce the oxidation state of an atom or ion in a compound using +number format e.g. +2 o Name transitional metal compounds from a given formula by applying oxidation numbers using roman numerals e.g. iron (III) oxide o Represent redox reactions using balanced half-equations and redox equations (acidic conditions only) o Communicate understanding, solve problems and make predictions using appropriate representations including half-equations and oxidation numbers 15 32. Deduce the oxidation state of nitrogen in NO3–. A. –5 B. -3 C. +3 D. +5 33. Which of the following is an example of a redox reaction? A. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) B. 2AgNO3(aq) + Na(s) → NaNO3(aq) + 2Ag(s) C. AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(aq) D. HCl(aq) + Na2(CO3)(aq) → NaCl(aq) + CO2(g) + H2O(l) 34. Identify the oxidising agent in the following redox reaction. 2S2O32-(aq) + I2(s) → S4O62-(aq) + 2I-(aq) A. I–(aq) B. I2(s) C. S4O62-(aq) D. S2O32-(aq) 35. A silver spoon becomes tarnished over time according to the following reaction. 4Ag(s) + O2(g) + 2H2S(g) → 2Ag2S(s) + 2H2O(l) Which row of the table correctly describes this process? 36. Redox reactions occur in the human body as well as in electrochemical cells. Nicotinamide adenine dinucleotide (NAD) is a vital coenzyme for energy production in the human body. It exists in two forms: an oxidised form, NAD+, and a reduced form, NADH. NAD is involved in the conversion of ethanol, CH3CH2OH, to ethanal, CH3CHO, in the human body. The overall equation for this redox reaction is CH3CH2OH + NAD+ → CH3CHO + NADH + H+ i. Write the two half-equations for this redox reaction. States are not required. ii. Identify the reducing agent in this redox reaction. 16 Electrochemical cells o Understand that electrochemical cells, including galvanic and electrolytic cells, consist of oxidation and reduction half-reactions connected via an external circuit that allows electrons to move from the anode (oxidation reaction) to the cathode (reduction reaction). o Understand that galvanic cells, including fuel cells, generate an electrical potential difference from a spontaneous redox reaction o Represent galvanic cells and fuel cells as cell diagrams including anode and cathode half- equations o Recognise that oxidation occurs at the negative electrode (anode) and reduction occurs at the positive electrode (cathode) o Explain how two half-cells can be connected by a salt bridge to create a voltaic cell (examples of half-cells are Mg, Zn, Fe and Cu and their solutions of ions) o Describe, using a diagram, the essential components of a galvanic cell; including the oxidation and reduction half-cells, the positive and negative electrodes and their solutions of their ions, the flow of electrons and the movement of ions, and the salt bridge. o Determine the relative strength of oxidising and reducing agents by comparing standard electrode potentials o Calculate cell potentials at standard conditions from standard electrode potentials o Compare cells constructed from different materials by comparing calculated cell potentials o Recognise the limitation associated with standard reduction potentials o Solve problems and make predictions about spontaneous reactions, including calculating cell potentials under standard condition o Understand that electrolytic cells use an external electrical potential difference to provide the energy to allow a non-spontaneous redox reaction to occur, and appreciate that these can be used in small-scale and industrial situations, including metal plating and the purification of copper o Predict and explain the products of the electrolysis of a molten salt and aqueous solutions of sodium chloride and copper sulfate (including both dilute and concentrated solutions of sodium chloride and copper sulfate). Explanations should refer to Eø values, the nature of the electrolyte and the concentration of the electrolyte o Describe, using a diagram, the essential components of an electrolytic cell; including source of electric current and conductors, positive and negative electrodes, and the electrolyte. 17 37. When molten sodium chloride, NaCl, is electrolysed, the product formed at the cathode is A. sodium liquid, Na. B. hydrogen gas, H2. C. chlorine gas, Cl2. D. oxygen gas, O2. 38. A galvanic cell is set up as shown in the diagram below. 39. When this cell is operating A. a gas forms at the Ag electrode. B. the mass of the Ag electrode increases. C. Ag+ ions move towards the Fe electrode. D. electrons move from the Ag electrode to the Fe electrode. 40. The silver oxide-zinc battery is rechargeable and utilises sodium hydroxide, NaOH, solution as the electrolyte. The battery is used as a backup in spacecraft, if the primary energy supply fails. The overall reaction during discharge is Zn + Ag2O → ZnO + 2Ag When the silver oxide-zinc battery is being recharged, the reaction at the anode is A. 2Ag + 2OH– → Ag2O + H2O + 2e– B. Ag2O + H2O + 2e– → 2Ag + 2OH– C. ZnO + H2O + 2e– → Zn + 2OH– D. Zn + 2OH– → ZnO + H2O + 2e– 18 41. The diagram below shows the structure of an electrolyser that produces hydrogen from renewable resources. The anode and cathode are separated by a selectively permeable membrane that allows the movement of ions. a) Identify the gas produced at the anode. b) Describe the characteristic of the ions that causes them to move across the permeable membrane. 42. The Daniell cell, a type of galvanic cell, was first constructed in the mid-1800s and this type of cell is still in use today. A diagram of the Daniell cell is shown below. i. Label the polarity of the electrodes by placing a positive (+) or negative (–) sign in each of the circles next to the electrodes on the diagram above. ii. Use the Standard electrode potentials from the Formula and Data Booklet to determine the theoretical voltage of this cell. iii. The electrolyte in the salt bridge is a potassium nitrate solution, KNO3(aq). In the box above the salt bridge, use an arrow to indicate the direction of flow of K+(aq) ions. iv. List two visible changes that are likely to be observed when the Daniell cell has been operating for some time. 19 43. The following diagrams represent combinations of four galvanic half-cells (G/G2+, J/J2+, Q/Q2+ and R/R2+) that were investigated under standard conditions. Each half-cell consisted of a metal electrode placed in a 1.0 M nitrate solution of the respective metal ion. The diagrams show the polarity of the electrodes in each half-cell, as determined using an ammeter. The results were then used to determine the order of the E0 values of the half-reactions. Which of the following indicates the order of the half-cell reactions, from the lowest E0 value to the highest? A. J/J2+, R/R2+, G/G2+, Q/Q2+ B. Q/Q2+, G/G2+, R/R2+, J/J2+ C. R/R2+, J/J2+, Q/Q2+, G/G2+ D. G/G2+, Q/Q2+, J/J2+, R/R2+ 44. The following diagram shows the electrolysis of a 0.5 M solution of copper(II) sulfate (CuSO4). a) Predict the product formed at the anode. b) Explain which product would be formed at the cathode. c) Identify one limitation associated with the use of standard reduction potentials. 20 45. The diagram below represents an electrochemical cell that has been constructed by connecting two half-cells. a) Identify the following by labelling the diagram above. the positive electrode (cathode) and negative electrode (anode) the direction of flow of electrons the movement of ions in the salt bridge b) Determine the standard electrode potential, Eo, for the cobalt(II)/cobalt half-cell above. 21 Unit 3 Multiple Topics 46. Phenolphthalein is an organic compound often used as an acid-base indicator. In its colourless form (H2In) it is a weak acid that dissociates in water to form pink anions (In2–). a) Determine the equilibrium equation for phenolphthalein. b) Identify the conjugate base in the equilibrium equation determined above. c) Explain why phenolphthalein does not change colour in an acidic solution when titrated with a small amount of NaOH. 22 Unit 4 Structure of organic compounds o Show the arrangements of atoms and bonding in organic molecules with structural formula (condensed and extended) o Recognise organic molecule functional groups including alkenes, alcohols, aldehydes, ketones, carboxylic acids, haloalkanes, esters, nitriles, amines and amides o Deduce the structural formulas and apply IUPAC rules in the nomenclature of organic compounds (parent chain up to 10 carbon atoms) with simple branching for alkanes, alkenes, alkynes, alcohols, aldehydes, ketones, carboxylic acids, haloalkanes, esters, nitriles, amines and amides o Identify structural isomers as compounds with the same molecular formula but different arrangement of atoms o Deduce the structural formulas and apply IUPAC rules in the nomenclature for isomers of the non-cyclic alkanes up to C6 o Identify stereoisomers as compounds with the same structural formula but with different arrangement of atoms in space o Describe and explain geometrical (cis and trans) isomerism in non-cyclic alkenes. 23 47. What is the IUPAC name for the molecule below? A. butyl ethanoate B. ethyl butanoate C. butyl ethanoic acid D. ethyl butanoic acid 48. Which structural formula represents pentan-2-one? 49. Which class of organic compound must contain at least three carbon atoms? A. Aldehydes B. Alkenes C. Carboxylic acids D. Ketones 24 50. Deduce which of the following is an isomer of the compound shown in the figure below. A. 1,2-dimethylpropane B. 2,2-dimethylpropane C. 2-methylbutane D. 3-methylbutane 51. Which one of the following is an isomer of pentanoic acid? A. CH3CHCH-O-CH2CHO B. CH2CHCH2-O-CH2CH2OH C. OHCCH2CH2CH2CHO D. CH3CHCHCH2COOH 52. The structural formulas of four alcohols are shown below. a) Determine which structure above (A, B, C or D) contains a tertiary carbon atom. b) Apply the IUPAC rules to name the secondary alcohol shown above. 53. Draw the structural formula of 2-methyl-propan-2-ol. 54. Give the molecular formula of but-2-yne. 55. Give the IUPAC name of the compound that has the structural formula shown below. 56. Which one of the following molecules contains a chiral carbon? A. CH2CHCH2CH3 B. CH2FCH2CH2Cl C. CH3CHOHCH2CH3 D. CH3CH2CFClCH2CH3 25 Physical properties and trends o Explain the characteristic physical properties of organic compounds including melting point, boiling point and solubility in water and organic solvents in terms of intermolecular forces (dispersion forces, dipole-dipole interactions and hydrogen bonds), which are influenced by the nature of the functional groups o Predict and explain the trends in melting and boiling point for members of a homologous series o Discuss the volatility and solubility in water of alcohols, aldehydes, ketones, carboxylic acids and halides. 26 57. All of the following compounds have similar molar masses. Which has the highest boiling point? A. Butane B. Ethanoic acid C. Propan-1-ol D. Propanone 58. The melting point of alkanes increases as the number of carbon atoms in the parent chain increases because the A. number of protons increases and therefore the strength of the intermolecular forces decreases. B. number of protons increases and therefore the strength of the intermolecular forces increases. C. number of electrons increases and therefore the strength of the intermolecular forces decreases. D. number of electrons increases and therefore the strength of the intermolecular forces increases. 59. A student wants to use a physical property to distinguish between two alcohols, octan-1-ol and propan-1-ol. Both alcohols are colourless liquids at standard laboratory conditions (SLC). The student should use A. density because propan-1-ol has a much higher density than octan-1-ol. B. boiling point because octan-1-ol has a higher boiling point than propan-1-ol. C. electrical conductivity because octan-1-ol has a higher conductivity than propan-1-ol. D. spectroscopy because it is not possible to distinguish between the alcohols using their physical properties. 60. The structural formulas of three organic compounds (ethanol, ethane and ethanoic acid) are shown below. Explain the relative solubility in water of these three molecules in terms of intermolecular forces. 27 61. Thiols are the sulfur analogues of alcohols in that the oxygen atom of the alcohol is replaced by a sulfur atom. For example, methanethiol (CH3SH) is the analogue of methanol (CH3OH). The boiling points of some straight chain alcohols and thiols are given in the following graph. Explain the patterns of the boiling points shown in the graph. 62. Pentane, pentanal and pentanoic acid all contain the same number of carbon atoms but display different physical properties. Their boiling points are given in the table below. Account for the difference in boiling points of the three compounds. 28 Organic reactions and reaction pathways o Appreciate that each class of organic compound displays characteristic chemical properties and undergoes specific reactions based on the functional group present; these reactions, including acid-base and oxidation reactions, can be used to identify the class of the organic compound o Distinguish between class and functional group, e.g. for OH, hydroxyl is the functional group whereas alcohol is the class. o Understand that saturated compounds contain single bonds only and undergo substitution reactions, and that unsaturated compounds contain double or triple bonds and undergo addition reactions o Determine the primary, secondary and tertiary carbon atoms in halogenoalkanes and alcohols and apply IUPAC rules of nomenclature o Describe, using equations: o oxidation reactions of alcohols and the complete combustion of alkanes and alcohols o substitution reactions of alkanes with halogens o substitution reactions of haloalkanes with halogens, sodium hydroxide, ammonia and potassium cyanide o addition reactions of alkenes with water, halogens and hydrogen halides o addition reactions of alkenes to form poly(alkenes) o Predict the major product of addition reactions with alkenes (with H2, Br2, H2O and HBr) using Markovnikov’s rule o Recall the acid-base properties of carboxylic acids and explain, using equations, that esterification is a reversible reaction between an alcohol and a carboxylic acid (hydrolysis) o Recognise the acid-base properties of amines and explain, using equations, the reaction with carboxylic acids to form amides o Recognise reduction reactions and explain, using equations, the reaction of nitriles to form amines and alkenes to form alkanes o Recognise and explain, using equations, that: o esters and amides are formed by condensation reactions o elimination reactions can produce unsaturated molecule and explain, using equations, the reaction of haloalkanes to form alkenes o Understand that organic reactions can be identified using characteristic observations and recall tests to distinguish between: o alkanes and alkenes using bromine water o primary, secondary and tertiary alcohols using acidified potassium dichromate (VI) and potassium manganate (VII) o Understand that the synthesis of organic compounds often involves constructing reaction pathways that may include more than one chemical reaction o Deduce reaction pathways, including reagents, condition and chemical equations, given the starting materials and the product. Conversions with more than two stages will not be assessed. o Reagents, conditions and equations should be included, e.g. the reaction of 1- bromopropane to 1-butylamine can be done in two stages: 1-bromopropane can be reacted with potassium cyanide to form butanenitrile, which can then be reduced by heating with hydrogen and a nickel catalyst to form 1-butylamine. 29 63. Which of the following undergoes a condensation reaction with an amine to form an amide? A. an alcohol B. an aldehyde C. a carboxylic acid D. a ketone 64. The structure of an organic compound is shown. Which row of the table correctly gives the name of the compound and one of the reactants used to produce it in a one-step reaction? Name Reactant Ethyl pentanoate Ethanol A. B. Ethyl pentanoate Pentan-1-ol C. D. Pent-1-yl ethanoate Ethanol Pent-1-yl ethanoate Pentan-1-ol 65. Identify the organic compound below that reacts with acidified potassium dichromate(VI) to produce a colour change from orange to green. A. (CH3)3COH B. CH3COOH C. CH3COCH3 D. CH3CH(OH)CH3 30 66. The following diagram represents a reaction pathway for the synthesis of Compound P. (i) Identify the starting substance, Compound M, by writing its condensed structural formula in the box provided. (ii) Identify the reagent(s) needed to convert propan-1-ol to propanoic acid, C2H5COOH, by writing the chemical formula(s) of the reagent(s) in the box provided. (iii) When C2H5COOH is mixed with ethanamine, CH3CH2NH2, in an acidified high-temperature environment, Compound P is formed. Write the condensed structural formula of Compound P in the box provided. 31 67. The following reaction scheme can be used to synthesise ethyl ethanoate. Outline the reagents and conditions required for each step. 68. The structural formulas for two amides are shown below. Explain how N-methylethanamide can be produced from an alcohol and any other organic compound(s) of your choice. Include conditions and reagents in your response. 32 69. Organic molecules have a hydrocarbon skeleton and can contain functional groups that are responsible for the molecules’ characteristic chemical properties. Complete the following tables by (i) writing the structural formula of each compound listed (ii) writing the structural formula of the organic product from the reaction (iii) naming the organic product from the reaction. When writing the structural formula, show the bonds between carbon atoms and within any functional group e.g. 33 34 Organic materials: structure and function o Explain the properties (including strength, density and biodegradability) of organic materials including proteins, carbohydrates, lipids and synthetic polymers by considering the primary, secondary and tertiary structures of the materials o Describe and explain the primary, secondary (α-helix and β-pleated sheets), tertiary and quaternary structure of proteins o Describe the characteristics of biological catalysts (enzymes) including that activity depends on the structure and the specificity of the enzyme action o Recognise that monosaccharides contain either an aldehyde group (aldose) or a ketone group (ketose) and several -OH groups, and have the empirical formula CH2O o Distinguish between α-glucose and β-glucose o Compare and explain the structural properties of starch (amylose and amylopectin) and cellulose o Recognise that triglycerides (lipids) are esters o Describe the difference in structure between saturated and unsaturated fatty acids o Describe, using equations, the base hydrolysis (saponification) of fats (triglycerides) to produce glycerol and its long chain fatty acid salt (soap), and explain how their cleaning action and solubility in hard water is related to their chemical structure o Explain how the properties of polymers depends on their structural features including; the degree of branching in polyethene (LDPE and HDPE), the position of the methyl group in polypropene (syntactic, isotactic and atactic) and polytetrafluorethene. 35 70. An increase in the amount of branching in the structure of polyethene A. increases its density and thus increases its melting point. B. decreases its density and thus increases its melting point. C. increases its density and thus decreases its melting point. D. decreases its density and thus decreases its melting point. 71. Carbohydrates are formed when A. glucose molecules are joined by glycosidic bonds. B. glucose molecules are joined by peptide bonds. C. amino acids are joined by glycosidic bonds. D. amino acids are joined by peptide bonds. 72. When insects touch a spider’s web they become stuck and therefore, easy prey for the spider. The insects become stuck because the web is coated with a glue-like substance produced by the spider. The ‘spider glue’ consists of water, proteins, ionic salts and polar carbon compounds. The structural formula given below shows a small section of a spider glue protein. a) List the names of the amino acids in the order in which they were drawn in the section of the protein given above. Do not use abbreviations. b) Circle one peptide bond in the above structure. c) What is the difference between the primary structure and the secondary structure of a protein? 73. The structure of a dipeptide is shown. a) Draw the structural formulae of the TWO amino acids from which this dipeptide was made. b) Explain how both forces and bonding are responsible for the tertiary structure of a protein. 74. Use a labelled diagram to show the structure of a soap molecule. 75. Explain how soap acts as a cleaning agent. 36 76. Detergents and soaps are both used as cleaning agents. The general structure of a detergent is given below. a) Explain how detergents are able to remove grease from a surface by referring to the intermolecular forces present. Include a labelled diagram to illustrate your answer. b) Detergents are considered to be more versatile cleaners than soap. Explain why soaps are generally less effective than detergents as cleaning agents in hard water. Include a relevant equation in your answer. c) Write an equation showing the formation of this soap from the fat (triglyceride) shown below. 37 Analytical techniques o Explain how proteins can be analysed by chromatography and electrophoresis o Select and use data from analytical techniques, including mass spectrometry, x-ray crystallography and infrared spectroscopy, to determine the structure of organic molecules o Analyse data from spectra, including mass spectrometry and infrared spectroscopy, to communicate conceptual understanding, solve problems and make predictions. 38 77. Analyse the infrared spectrum below to determine the functional groups present and the homologous series of the molecule in the sample. 78. The diagram shows the mass spectrum of an organic compound. Which compound was analysed? A. Butan-1-amine B. Butanoic acid C. Ethanoic acid D. Iron(II) sulfide 39 79. A chemical that contains carbon, C, nitrogen, N, and hydrogen, H, in the ratio 4:1:11 is analysed using spectroscopy. a) The infra-red (IR) spectrum of the chemical is shown below. In the table below, write the bond responsible for the wave numbers given. Wave number (cm–1) Bond 2956 3376 b) The mass spectrum of the chemical is shown below. i. What is the molecular formula for the parent molecule? Justify your answer using information from the mass spectrum. ii. Identify the fragment that produces the base peak. iii. Draw the structural formulas for two possible structural isomers of the chemical, which are consistent with the mass spectrum and the IR spectrum. 40 Chemical synthesis o Appreciate that chemical synthesis involves the selection of particular reagents to form a product with specific properties o Understand that reagents and reaction conditions are chosen to optimise the yield and rate for chemical synthesis processes, including the production of ammonia (Haber process), sulfuric acid (contact process) and biodiesel (base-catalysed and lipase-catalysed methods) o Understand that fuels, including biodiesel, ethanol and hydrogen, can be synthesised from a range of chemical reactions including, addition, oxidation and esterification o Understand that enzymes can be used on an industrial scale for chemical synthesis to achieve an economically viable rate, including fermentation to produce ethanol and lipase- catalysed transesterification to produce biodiesel o Describe, using equations, the production of ethanol from fermentation and the hydration of ethene o Describe, using equations, the transesterification of triglycerides to produce biodiesel o Discuss, using diagrams and relevant half-equations, the operation of a hydrogen fuel cell under acidic and alkaline conditions. o Calculate the yield of chemical synthesis reactions by comparing stoichiometric quantities with actual quantities and by determining limiting reagents. 41 80. The Haber process combines nitrogen and hydrogen to produce ammonia as shown in the reaction below. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = -92 kJ mol–1 Which of the following conditions favours the formation of the highest yield of ammonia from an equilibrium mixture of nitrogen and hydrogen? A. high temperature and high pressure B. high temperature and low pressure C. low temperature and high pressure D. low temperature and low pressure 81. Which one of the following statements about catalysis in the production of biodiesel is correct? A. Base catalysis generally has a higher reaction rate but, unlike lipase catalysis, can cause saponification, which decreases the biodiesel yield. B. The sodium hydroxide and potassium hydroxide used in base catalysis are readily available and relatively cheap, but lipase catalysis produces more toxic waste water. C. Base catalysis involves only one step, while lipase catalysis involves many steps in its synthesis sequence, which in turn adds to the cost of the process. D. Base catalysis typically has a lower rate and yield of biodiesel but lipase catalysis is sensitive to alcohols, such as methanol, and has higher energy costs. 82. The contact process is an important industrial process for making sulfuric acid (H2SO4). This process occurs in three stages. Stage 1: sulfur + oxygen sulfur dioxide S(s) + O2(g) → SO2(g) Stage 2: sulfur dioxide + oxygen sulfur trioxide 2SO2(g) + O2(g) ⇌ 2SO3(g) Stage 3: sulfur trioxide + water sulfuric acid SO3(g) + H2O(l) → H2SO4(l) a) Explain which stage of the process would be affected by a change in pressure. b) Calculate the mass of sulfur required to produce 1100 kg of sulfuric acid if the yield of sulfur trioxide in the contact process is 97%. Show your working. 42 83. An energy company investigates the feasibility of supplying energy while reducing greenhouse gas emissions. Solar panels collect energy from the sun during daylight hours and this energy is used to electrolyse water, H2O, to produce oxygen gas, O2, and hydrogen gas, H2. These gases are stored separately and then used in a fuel cell to produce energy when required. The diagram below shows a simplified representation of the set-up used. a) State the polarity of Electrode W in the electrolysis cell. b) The fuel cell operates in an alkaline environment. Write the half-equation for the reaction that takes place at Electrode Y. 84. The diagram below represents a hydrogen fuel cell that uses hydrogen gas and oxygen gas to produce electricity. a) With reference to Zones A1 and A2, B, C and D, use the diagram above to discuss the operation of a hydrogen fuel cell with an alkaline electrolyte. b) Determine the oxidation and reduction half-equations and the overall reaction for the hydrogen fuel cell. 43 Green chemistry o Appreciate that green chemistry principles include the design of chemical synthesis processes that use renewable raw materials, limit the use of potentially harmful solvents and minimise the amount of unwanted products o Outline the principles of green chemistry and recognise that the higher the atom economy, the ‘greener’ the process o Calculate atom economy and draw conclusions about the economic and environmental impact of chemical synthesis processes. 44 85. The equation for the production of nitrous oxide, 2N2(g) + O2(g) → 2N2O(g), shows a high atom economy because A. all the atoms in the reactants are converted to the desired product. B. three molecules of reactant produce two molecules of product. C. two diatomic molecules are combined to form a compound. D. two different reactants are combined to form one product. 86. Calculate the atom economy for magnesium sulfate as the desired product in the following reaction. Mg(s) + H2SO4(aq) → H2(g) + MgSO4(aq) A. 19.9% B. 20.2% C. 81.5% D. 98.4% 45 Macromolecules: polymers, proteins and carbohydrates o Describe, using equations, how addition polymers can be produced from their monomers including polyethene (LDPE and HDPE), polypropene and polytetrafluorethene o Describe, using equations, how condensation polymers, including polypeptides (proteins), polysaccharides (carbohydrates) and polyesters, can be produced from their monomers o Discuss the advantages and disadvantages of polymer use, including strength, density, lack of reactivity, use of natural resources and biodegradability o Describe the condensation reaction of 2-amino acids to form polypeptides (involving up to three amino acids), and understand that polypeptides (proteins) are formed when amino acid monomers are joined by peptide bonds o Describe the condensation reaction of monosaccharides to form disaccharides (lactose, maltose and sucrose) and polysaccharides (starch, glycogen and cellulose), and understand that polysaccharides are formed when monosaccharides monomers are joined by glycosidic bonds. 46 87. Which of the following monomers undergoes polymerisation to form polytetrafluorethene? 88. Describe how glucose monomers combine to form a branched glycogen polymer. 89. Pure antimony(III) oxide is used as a catalyst in the production of polyethylene terephthalate (PET). a) Draw the monomers required to produce this polymer. b) State one common use for PET and state two properties that enable it to be used for this purpose. c) PET is produced through condensation polymerisation; another type of polymer is produced through addition polymerisation. Each of these types of polymerisation uses different types of monomers. Distinguish between the types of monomers used for each type of polymerisation. 47 Molecular manufacturing o Appreciate that molecular manufacturing processes involve the positioning of molecules to facilitate a specific chemical reaction; such methods have the potential to synthesise specialised products, including proteins, carbon nanotubes, nanorobots and chemical sensors used in medicine. 48 90. In molecular manufacturing, mechanosynthesis (or the orientation effect) produces molecules with specific properties by A. adding or substituting specific atoms in a structure. B. positioning desired functional groups so they align in molecules. C. adding a protective group that prevents functional groups from reacting. D. manipulating the bonding that occurs between atoms, ions and molecules. 49 Unit 4 Multiple Topics 91. Enzymes are globular proteins that can act as biological catalysts, with enzyme-catalysed reactions playing an important role in chemical industry. a) Describe three characteristics of biological catalysts (enzymes). b) Use a balanced chemical equation to describe the lipase-catalysed transesterification of triglyceride to produce biodiesel. 92. Proteins can be hydrolysed to produce a mixture of amino acids, which can be separated using electrophoresis as shown below. a) Explain how a mixture of alanine (Ala) and lysine (Lys) can be separated using electrophoresis and a buffer solution of pH 7. b) In the space below, apply your understanding to draw the structural formula of the dipeptide formed by the condensation reaction of Ala and Lys. c) Explain the secondary structure of proteins. 50 Units 3 and 4 Multiple Topics 93. When a carboxylic acid is reacted with an alcohol and an acid catalyst, an ester and water are formed by the reversible reaction shown below. a) Use a balanced chemical equation for the hydrolysis of methyl ethanoate to explain that esterification is a reversible reaction. b) Calculate the concentration of each of the components of the esterification reaction in (a) at equilibrium if both the carboxylic acid and the alcohol had initial concentrations of 0.25 mol L–1. The equilibrium constant (Kc) for the reaction is 4.0. 51 References Queensland Curriculum and Assessment Authority (2019), Chemistry General Senior Syllabus 2019 v1.3 Accessed June 2020 at https://www.qcaa.qld.edu.au/senior/senior- subjects/sciences/chemistry/syllabus Queensland Curriculum and Assessment Authority (2020), Chemistry Sample External Exam Paper 2020 Accessed June 2020 at https://www.qcaa.qld.edu.au/senior/senior- subjects/sciences/chemistry/assessment NSW Government Education Standards Authority (2018 and 2019), Chemistry Higher School Certificate Examination Accessed June 2020 at https://educationstandards.nsw.edu.au/wps/portal/nesa/11-12/resources/hsc-exam-papers Victorian Curriculum and Assessment Authority (2018 and 2019), VCE Chemistry Examination Accessed June 2020 at https://www.vcaa.vic.edu.au/assessment/vce-assessment/past- examinations/Pages/Chemistry.aspx Western Australia School Curriculum and Standards Authority (2017, 2018 and 2019) Chemistry ATAR Examination Accessed June 2020 at https://senior-secondary.scsa.wa.edu.au/further- resources/past-atar-course-exams/chemistry-past-atar-course-exams 52