Skill Align ACT BSSS Chemistry T - Free Online Pack 0
An independently authored, adaptable school-style assessment with worked answers and question-specific marking guidance.
- Paper
- Integrated practice assessment
- Reading
- Teacher-set
- Writing
- Suggested 120 minutes
- Assessment
- 100 marks
No centrally prescribed ACT BSSS examination reference sheet is claimed. Required constants, electrode potentials and molar masses are supplied where needed.
Part A - Multiple choice
Questions 1 to 15 (15 marks). Select the best answer for each question.
Question 1
1 mark- Both reactions have stopped because the concentrations are constant.
- Only N₂O₄ molecules remain once equilibrium is reached.
- The forward and reverse reactions continue at equal rates while concentrations remain constant.
- The forward rate is greater than the reverse rate at equilibrium.
Question 2
1 mark- Immediately after compression, Qp is smaller than Kp, so the net reaction proceeds towards NH₃ until equilibrium is re-established.
- The equilibrium constant increases and the system shifts towards NH₃.
- The system shifts towards N₂ and H₂ because collisions become less frequent.
- There is no shift because all gases are compressed equally.
Question 3
1 mark- Products and reactants have equal concentrations.
- Products predominate at equilibrium.
- The reaction cannot reach equilibrium.
- Reactants predominate at equilibrium.
Question 4
1 mark- H₂O
- CH₃COO⁻
- H₃O⁺
- OH⁻
Question 5
1 mark- 2.60
- 1.60
- 3.40
- 11.40
Question 6
1 mark- The lowest available pH range, regardless of the curve.
- A range entirely above pH 12.
- Any range because indicators do not respond to pH.
- A range that lies within the steep pH change around the equivalence point.
Question 7
1 mark- 0.1000
- 9.000
- 10.00
- 100.0
Question 8
1 mark- Zn²⁺(aq) + 2e⁻ → Zn(s)
- Zn(s) → Zn²⁺(aq) + 2e⁻
- Zn(s) + 2e⁻ → Zn²⁺(aq)
- Zn²⁺(aq) → Zn(s) + 2e⁻
Question 9
1 mark- -1.10 V
- +1.10 V
- +0.42 V
- -0.42 V
Question 10
1 mark- It permits ion migration that maintains electrical neutrality in each half-cell.
- It supplies electrons to the cathode.
- It increases the standard electrode potentials.
- It prevents all mixing and all ion movement.
Question 11
1 mark- -CONH-
- -OH
- -COO-
- -NH₂
Question 12
1 mark- Eight carbon atoms
- An O-H bond
- A base peak intensity of 88%
- A relative molecular mass of 88
Question 13
1 mark- 75.0%
- 25.0%
- 133%
- 3.00%
Question 14
1 mark- Use a larger excess of every reagent.
- Increase the reaction temperature without measuring energy use.
- Discard the aqueous phase after every trial.
- Replace a toxic volatile solvent with a safer recyclable solvent while maintaining performance.
Question 15
1 mark- Only the colour of the product
- Only the manufacturer's advertising claim
- Verified life-cycle emissions, energy source, yield, cost and local environmental impacts
- The highest single-trial yield with no uncertainty
Part B - Short response
Questions 16 and 17 (20 marks). Show chemical reasoning, equations and working.
Question 16
10 marksAt 450 °C, a 2.00 L vessel contains an equilibrium mixture for N₂(g) + 3H₂(g) ⇌ 2NH₃(g): 0.400 mol N₂, 0.600 mol H₂ and 0.200 mol NH₃. The forward reaction is exothermic.
Question 17
10 marksA galvanic cell uses Zn(s)|Zn²⁺(aq) and Cu²⁺(aq)|Cu(s) half-cells at standard conditions. E°(Zn²⁺/Zn) = -0.76 V and E°(Cu²⁺/Cu) = +0.34 V.
Part C - Data analysis
Question 18 (20 marks). Analyse the supplied chemical evidence and justify conclusions.
Question 18
20 marksA student dilutes 10.00 mL vinegar to 100.0 mL. Three 20.00 mL aliquots of the diluted solution require 16.20, 16.25 and 16.15 mL of 0.1000 mol L⁻¹ NaOH. Accept a set of titres as concordant when the maximum difference between them is no greater than 0.10 mL. This is a permitted spread, not a measurement uncertainty. CH₃COOH + NaOH → CH₃COONa + H₂O. M(CH₃COOH) = 60.05 g mol⁻¹; vinegar density = 1.00 g mL⁻¹.
Part D - Practical investigation
Question 19 (20 marks). Apply science inquiry skills to the investigation.
Question 19
20 marksStudents investigate the effect of temperature on the equilibrium Fe³⁺(aq) + SCN⁻(aq) ⇌ FeSCN²⁺(aq). They prepare identical sealed samples, equilibrate them at 10, 20, 30, 40 and 50 °C, then measure absorbance at the complex's absorption maximum.
Part E - Extended response
Question 20 (25 marks). Integrate chemistry, evidence, context and justified evaluation.
Question 20
25 marksA hospital network is comparing two aspirin routes. Route A uses salicylic acid and excess ethanoic anhydride with a phosphoric acid catalyst, 80 °C heating and solvent recrystallisation; it gives 82% purified yield and 75.0% atom economy, with solvent recovery. Route B uses salicylic acid, ethanoyl chloride and one stoichiometric equivalent of pyridine, which is converted to pyridinium chloride and is included in the atom-economy denominator. Route B uses a chlorinated solvent at 25 °C, gives 91% yield and 60.9% atom economy, and produces chloride-containing waste. Decision-makers must consider medicine quality, worker safety, waste, energy and cost.
Worked Solutions And Marking Guide
General marking principles
- Award each one-mark criterion independently for the specific chemical evidence described.
- Accept equivalent scientifically accurate equations, structures, calculations or reasoning applied to the supplied context.
- Carry forward an earlier numerical error when later chemistry is internally consistent, unless a later criterion independently assesses that step.
- Use the task-specific evidence analytically across Concepts, Models and Applications, Contexts, and Inquiry Skills.
Question 1
Answer: The forward and reverse reactions continue at equal rates while concentrations remain constant.
Dynamic equilibrium has equal forward and reverse rates; macroscopic concentrations are constant, not necessarily equal.
Question 2
Answer: Immediately after compression, Qp is smaller than Kp, so the net reaction proceeds towards NH₃ until equilibrium is re-established.
If every partial pressure is multiplied by f > 1, Qp is divided by f² because there are two product gas moles and four reactant gas moles. Therefore Qp initially becomes smaller than Kp and the reaction proceeds towards NH₃. Kp is unchanged because temperature is constant.
Question 3
Answer: Reactants predominate at equilibrium.
A small equilibrium constant indicates that the equilibrium position lies mainly towards reactants.
Question 4
Answer: CH₃COO⁻
CH₃COOH loses one proton to form its conjugate base, CH₃COO⁻.
Question 5
Answer: 2.60
HCl is a strong monoprotic acid, so [H₃O+] = 2.5 × 10⁻³ mol L⁻¹ and pH = -log10[H₃O+] = 2.60.
Question 6
Answer: A range that lies within the steep pH change around the equivalence point.
An indicator must change colour within the rapid pH change near equivalence so the endpoint closely estimates equivalence.
Question 7
Answer: 10.00
The dilution factor is final volume divided by aliquot volume: 100.0/10.00 = 10.00.
Question 8
Answer: Zn(s) → Zn²⁺(aq) + 2e⁻
Oxidation is electron loss, so neutral Zn forms Zn²⁺ and releases two electrons.
Question 9
Answer: +1.10 V
E°cell = E°cathode - E°anode = 0.34 - (-0.76) = +1.10 V.
Question 10
Answer: It permits ion migration that maintains electrical neutrality in each half-cell.
Salt-bridge ions migrate to prevent charge build-up, completing the internal circuit without carrying electrons.
Question 11
Answer: -COO-
An ester contains a carbonyl carbon bonded to an oxygen, represented by -COO-.
Question 12
Answer: A relative molecular mass of 88
For a singly charged intact molecular ion, m/z equals the molecular mass in relative mass units.
Question 13
Answer: 75.0%
Percentage yield = (9.00/12.0) × 100 = 75.0%.
Question 14
Answer: Replace a toxic volatile solvent with a safer recyclable solvent while maintaining performance.
Reducing solvent hazard and recovering the solvent lowers waste and exposure while preserving the intended chemistry.
Question 15
Answer: Verified life-cycle emissions, energy source, yield, cost and local environmental impacts
A sustainability decision needs credible chemical performance plus environmental, economic and contextual evidence.
Question 16
(a) [N₂] = 0.200 mol L⁻¹, [H₂] = 0.300 mol L⁻¹ and [NH₃] = 0.100 mol L⁻¹. Kc = [NH₃]²/([N₂][H₂]³) = 1.85 L² mol⁻².
(b) Cooling favours the exothermic forward reaction, so the equilibrium NH₃ yield increases. Because temperature changes, Kc increases for this exothermic reaction.
Detailed marking criteria
Part a (1 mark)
States the correct Kc numerator [NH₃]².
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
States the correct denominator [N₂][H₂]³.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Converts every supplied amount to concentration using 2.00 L.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Substitutes 0.100²/(0.200 × 0.300³).
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Obtains Kc = 1.85 L² mol⁻² to three significant figures.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Identifies the forward reaction as the heat-producing direction.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
States that cooling favours the forward direction.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Predicts an increased equilibrium amount or yield of NH₃.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
States that Kc changes because temperature changes.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
States that Kc increases when this exothermic system is cooled.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Question 17
(a) Zn is the anode; Cu is the cathode; electrons flow through the external wire from Zn to Cu. Zinc atoms are oxidised to Zn²⁺, releasing electrons at the anode. Cu²⁺ ions are reduced to copper metal, consuming electrons at the cathode.
(b) Zn(s) → Zn²⁺(aq) + 2e⁻; Cu²⁺(aq) + 2e⁻ → Cu(s); Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s); E°cell = +1.10 V.
Detailed marking criteria
Part a (1 mark)
Identifies Zn as the anode.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Identifies Cu as the cathode.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
States the complete external electron-flow direction from Zn to Cu; award this direction mark once only.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Explains that oxidation of zinc atoms to Zn²⁺ releases electrons at the anode.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Explains that reduction of Cu²⁺ to copper metal consumes electrons at the cathode.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Writes the balanced zinc oxidation half-equation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Writes the balanced copper(II) reduction half-equation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Combines them into the balanced overall ionic equation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Uses E°cell = E°cathode - E°anode.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Calculates E°cell = +1.10 V with sign and unit.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Question 18
(a) Mean titre = (16.20 + 16.25 + 16.15)/3 = 16.20 mL. The maximum difference is 16.25 - 16.15 = 0.10 mL. It equals the permitted maximum spread, so all three trials are concordant and no exclusion is justified.
(b) n(NaOH) = 0.1000 × 0.01620 = 1.620 × 10⁻³ mol. The 1:1 ratio gives 1.620 × 10⁻³ mol CH₃COOH in 20.00 mL, so the diluted concentration is 0.08100 mol L⁻¹ and the original concentration is 0.8100 mol L⁻¹.
(c) In 1.000 L, m(CH₃COOH) = 0.8100 × 60.05 = 48.64 g. The 1.000 L vinegar mass is 1000 g, so percentage by mass = 4.864% ≈ 4.86%.
(d) The recorded titre and calculated NaOH moles would be too high, so the calculated vinegar concentration would be systematically too high. Check delivered volumes gravimetrically using water and a calibrated balance, or compare the burette with a calibrated volumetric standard.
Detailed marking criteria
Part a (1 mark)
Adds the three titres correctly.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Divides by three to obtain 16.20 mL.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Calculates the 0.10 mL maximum difference.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Compares that difference with the stated maximum spread of 0.10 mL, including equality.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Concludes that all three trials are concordant with no justified exclusion.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Converts 16.20 mL to 0.01620 L.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Calculates 1.620 × 10⁻³ mol NaOH.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Uses the 1:1 mole ratio.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Calculates 0.08100 mol L⁻¹ for the diluted vinegar.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Applies the factor of ten to obtain 0.8100 mol L⁻¹.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Uses 0.8100 mol for a 1.000 L basis.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Multiplies by 60.05 g mol⁻¹.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Obtains 48.64 g ethanoic acid per litre.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Uses density to obtain 1000 g vinegar per litre.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Calculates 4.86% by mass to three significant figures.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Identifies the delivered-volume error as systematic.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
States that each recorded titre is 0.20 mL too high.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Links the inflated titre to excessive calculated NaOH moles.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Concludes that acid concentration is overestimated.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Proposes a gravimetric or volumetric calibration check capable of detecting the delivered-volume bias.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Question 19
(a) Hypothesis: increasing temperature will change equilibrium [FeSCN²⁺] and therefore absorbance. Independent variable: temperature. Dependent variable: equilibrium absorbance (or calculated [FeSCN²⁺]).
(b) Use identical initial Fe³⁺ and SCN⁻ concentrations and volumes; sealed matched cuvettes; the same wavelength and calibrated spectrophotometer; sufficient equilibration time; and repeated independent samples at every temperature.
(c) For example, wear splash goggles to protect eyes from irritating solution splashes, and handle hot water-bath vessels with suitable tongs to reduce burn risk. Collect iron/thiocyanate waste in a compatible labelled chemical-waste container for authorised treatment, preventing uncontrolled release to drains. Suitable gloves, capped small-volume samples or other justified controls can replace either safety example; only two safety measures and one explained disposal measure are required.
(d) Replicates estimate random variation and reveal anomalies; means with spread show reliability. A calibration curve converts absorbance to concentration within a verified linear range, allowing quantitative comparison rather than assuming equal response at all concentrations.
Detailed marking criteria
Part a (1 mark)
States a directional or change-based testable relationship.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Links the hypothesis to equilibrium FeSCN²⁺ concentration.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Identifies temperature as the independent variable.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Identifies equilibrium absorbance as the measured dependent variable.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Connects absorbance to FeSCN²⁺ concentration.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Controls initial Fe³⁺ concentration.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Controls initial SCN⁻ concentration and total volume.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Uses sealed matched vessels to prevent composition changes.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Uses the same calibrated wavelength/instrument settings.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Allows equal equilibration time and includes replication.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Identifies a first feasible safety measure for this investigation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Explains the specific hazard reduced by the first measure.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Identifies a different feasible safety measure for this investigation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Explains the specific hazard reduced by the second measure.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Explains one responsible disposal procedure that contains the iron/thiocyanate waste and prevents uncontrolled environmental release.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
States that replication exposes random variation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
States that replication helps identify anomalies.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Uses a mean and spread to judge reliability.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Explains that calibration converts absorbance to concentration.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Requires use within the validated linear calibration range.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Question 20
(a) Route A forms an ester by acylating the phenolic oxygen of salicylic acid. Ethanoic anhydride is the acylating reagent and supplies the ethanoyl group. The phenolic -OH becomes -OCOCH₃ while the carboxylic-acid group remains unchanged.
(b) The order represents 150.0/180.16 = 0.8326 kmol purified aspirin. Required salicylic acid = 0.8326/0.82 = 1.015 kmol, approximately 1.02 kmol. The available 1.00 kmol produces only 0.82 × 180.16 = 147.7 kg, a 2.27 kg shortfall, so the order cannot be met at the stated yield.
(c) B has the higher yield and lower heating demand, but A has higher atom economy, avoids ethanoyl chloride, stoichiometric pyridine and chlorinated-solvent hazards, produces less chloride-containing waste and recovers solvent. A's heating cost must be weighed against B's hazardous-material and waste-treatment burdens.
(d) Any two independently informative, justified checks are acceptable. For example, chromatography alongside authenticated aspirin and salicylic-acid standards should show an aspirin match and no resolved starting-material spot or peak, while a narrow melting range matching pure aspirin provides a different physical-property check. IR may replace either: reference matching should show the ester C=O/C-O pattern and loss of phenolic O-H, while aspirin retains carboxylic-acid O-H. A suitable mass spectrum or another justified structural/purity test is also valid. Agreement across different properties strengthens identification; neither a single chromatographic match nor appearance alone proves purity.
(e) Prefer Route A provisionally because its 75.0% atom economy, lower intrinsic reagent/solvent hazard, reduced chloride waste and solvent recovery outweigh the moderate yield and heating disadvantages, provided pharmaceutical purity is equivalent. A pilot life-cycle and cost study should measure actual solvent-recovery efficiency, energy source, waste treatment and batch purity before procurement.
Detailed marking criteria
Part a (1 mark)
Identifies ester formation by acylation or a chemically equivalent reaction description.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Identifies ethanoic anhydride as the acylating reagent.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Explains that an ethanoyl group is transferred.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Locates the conversion at the phenolic oxygen.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part a (1 mark)
Identifies the retained carboxylic-acid functional group.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Converts the order to 0.8326 kmol purified aspirin using its molar mass.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Divides the required product amount by the 0.82 isolated-yield factor rather than multiplying.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Obtains a minimum salicylic-acid requirement of about 1.015 kmol using 1:1 stoichiometry.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Calculates the available-feed output as about 147.7 kg.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part b (1 mark)
Concludes that the 150.0 kg order cannot be met and quantifies the approximately 2.27 kg shortfall.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Compares 91% and 82% yields correctly.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Compares 75.0% and 60.9% atom economies correctly.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Identifies Route B's greater reagent or solvent hazard.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Identifies Route B's pyridinium-chloride or chloride-waste burden.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part c (1 mark)
Recognises Route A's heating demand and solvent-recovery benefit.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Selects a first scientifically suitable identity or purity check.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Explains its expected aspirin-versus-salicylic-acid observation using authenticated reference evidence.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Selects a second scientifically suitable check probing a different property.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Explains the second expected observation using an appropriate reference or standard.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part d (1 mark)
Explains why the two checks provide independently informative evidence supporting aspirin identity rather than unreacted starting material.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part e (1 mark)
Makes an explicit route recommendation.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part e (1 mark)
Uses at least one quantitative performance comparison.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part e (1 mark)
Uses worker-safety or hazard evidence.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part e (1 mark)
Uses waste, resource or energy evidence.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Part e (1 mark)
Identifies a decision-relevant evidence gap and a feasible way to resolve it.
Acceptable alternatives: Accept a chemically equivalent representation that preserves the assessed proposition.
Diagnostic Checklist
| Topic | Questions | Marks | Marks Lost | Action |
|---|---|---|---|---|
| Acids, bases and volumetric analysis | Q4 (1 mark), Q5 (1 mark), Q6 (1 mark), Q7 (1 mark), Q18(b) (5 marks), Q18(c) (5 marks) | 14 | ___ | Review Brønsted-Lowry reactions, pH, indicators, equivalence and volumetric calculations. |
| Equilibrium systems | Q1 (1 mark), Q2 (1 mark), Q3 (1 mark), Q16(a) (5 marks), Q16(b) (5 marks) | 13 | ___ | Review dynamic equilibrium, equilibrium constants and responses to concentration, pressure and temperature changes. |
| Organic structure and analysis | Q11 (1 mark), Q12 (1 mark), Q20(d) (5 marks) | 7 | ___ | Review functional groups, organic reactions, structure-property relationships and instrumental evidence. |
| Redox and electrochemistry | Q8 (1 mark), Q9 (1 mark), Q10 (1 mark), Q17(a) (5 marks), Q17(b) (5 marks) | 13 | ___ | Review oxidation states, half-equations, cell potentials, galvanic cells, electrolysis and fuel cells. |
| Science as a Human Endeavour | Q15 (1 mark), Q20(e) (5 marks) | 6 | ___ | Review model development, collaboration, impacts, risks and evidence-informed sustainability decisions. |
| Science inquiry skills | Q18(a) (5 marks), Q18(d) (5 marks), Q19(a) (5 marks), Q19(b) (5 marks), Q19(c) (5 marks), Q19(d) (5 marks) | 30 | ___ | Review safe experimental design, data representation, uncertainty, validity and evidence-based conclusions. |
| Synthesis and design | Q13 (1 mark), Q14 (1 mark), Q20(a) (5 marks), Q20(b) (5 marks), Q20(c) (5 marks) | 17 | ___ | Review synthesis pathways, reagents, conditions, yields, polymers, fuels and green chemistry. |