AQA A-Level Chemistry Paper 2, 2021
Every question from AQA A-Level Chemistry Paper 2, 2021: 9 questions, 98 marks, each with its mark scheme and topic.
- Question 1 15 marks
This question explores the chemistry of triesters found in coconut oil, focusing on their hydrolysis with KOH. Students must complete a reaction to show the formation of glycerol, identify and give a use for carboxylate salts (soaps), and deduce the structure of the alkyl chains from molecular mass data. There is a calculation to find the percentage by mass of triester in a sample using titration data, and a final question on solvent choice and safety precautions during heating.
Physical Chemistry · Organic Chemistry · Required Practicals · 3.1.2 Amount of Substance · 3.3.9 Carboxylic Acids and Derivatives · Required Practical 5: Distillation of a product from a reaction
- Question 2 19 marks
This question explores fuels, particularly petrol and its production. It begins by testing understanding of the term “fraction” in crude oil processing. It then focuses on cracking hexadecane into smaller hydrocarbons like hexane and cyclopentane, and naming an appropriate catalyst. It moves into the environmental impact of burning fuels, explaining how carbon dioxide absorbs infrared radiation. A reaction mechanism is analysed for carbon capture using 2-aminoethanol, followed by structural and bonding analysis of protonated and unprotonated amine groups. Finally, bioethanol as a carbon-neutral alternative fuel is evaluated, including its production, relevant equations, and environmental trade-offs.
Organic Chemistry · 3.3.2 Alkanes · 3.3.5 Alcohols · 3.3.14 Organic Synthesis
- Question 3 7 marks
This question assesses students' understanding of experimental design and data accuracy when determining the enthalpy of combustion. It begins by asking for a suitable table to record necessary measurements (temperature and mass of fuel burnt). Students must then critique the use of less effective equipment (glass beaker vs. copper calorimeter), and identify why experimental results tend to be less exothermic than theoretical values. Finally, it tests their ability to suggest improvements to the apparatus setup to enhance accuracy.
Required Practicals · Physical Chemistry · Required Practical 2: Measurement of an enthalpy change · 3.1.4 Energetics
- Question 4 9 marks
Benzene Structure and Electrophilic Substitution This question explores the thermodynamic stability of benzene through enthalpy calculations and diagrams, comparing the actual delocalised structure to Kekulé's model. It involves calculating enthalpy changes using bond enthalpies and interpreting why benzene is more stable due to electron delocalisation. The latter part focuses on naming and completing the electrophilic substitution mechanism for the nitration of benzene, showing all necessary curly arrows and lone pairs across multiple steps.
Organic Chemistry · Physical Chemistry · 3.3.10 Aromatic Chemistry · 3.1.4 Energetics
- Question 6 7 marks
Isomerism and Spectroscopy in C₅H₁₀O This question explores structural and stereoisomerism in molecules with molecular formula C₅H₁₀O, including identification of optically active and geometric (E/Z) isomers. Students are also tested on their ability to distinguish enantiomers experimentally using polarimetry, and apply NMR spectral data to deduce structures of cyclic ether isomers.
Organic Chemistry · 3.3.15 Nuclear Magnetic Resonance Spectroscopy · 3.3.7 Optical Isomerism
- Question 7 9 marks
Spectroscopy and Structure Determination This question explores the use of spectroscopy to identify organic compounds. Part (a) involves interpreting an infrared (IR) spectrum of a compound with molecular formula C₄H₈O, where students must identify the functional group. In part (b), another compound (C₄H₇NO) is reduced, and students must describe how the IR spectrum changes. Part (c) tests interpretation of proton NMR data for C₃H₇ClO, where students analyse chemical shifts, integration values, and splitting patterns to deduce the structure.
Organic Chemistry · 3.3.6 Organic Analysis · 3.3.15 Nuclear Magnetic Resonance Spectroscopy
- Question 8 13 marks
Functional Group Identification and Structural Deduction This question focuses on the use of chemical tests to identify functional groups such as aldehydes, ketones, and carboxylic acids. Students are required to interpret qualitative results from reagents like acidified dichromate, Tollens’ reagent, and sodium carbonate, and use this evidence to deduce the structure of an unknown organic compound.
Organic Chemistry · 3.3.14 Organic Synthesis · 3.3.9 Carboxylic Acids and Derivatives · 3.3.5 Alcohols · 3.3.4 Alkenes
- Question 9 7 marks
Ozone Layer Chemistry and Radical Mechanisms This question focuses on the role of the ozone layer in protecting life from harmful UV radiation and how chlorofluorocarbons (CFCs) decompose to form chlorine radicals. It tests understanding of radical chain reactions, including catalytic ozone depletion and propagation steps in radical substitution reactions involved in forming hydrochlorofluorocarbons (HCFCs).
Organic Chemistry · 3.3.2 Alkanes · 3.3.3 Halogenoalkanes
- Question 10 12 marks
Rates of Reaction and Activation Energy This question explores the kinetics of the iodine–propanone reaction in acid, including experimental techniques to determine the order of reaction with respect to iodine. Students analyse a graph of iodine concentration over time to identify zero-order behaviour, then calculate activation energy using the Arrhenius equation and a graph of ln k against 1/T.
Physical Chemistry · Required Practicals · 3.1.9 Rate Equations · Required Practical 7: Measuring the rate of reaction by an initial rate method