AQA A-Level Chemistry Paper 3, 2021
Every question from AQA A-Level Chemistry Paper 3, 2021: 34 questions, 84 marks, each with its mark scheme and topic.
- Question 1 20 marks
Polyesters, Titration & Thermodynamics with Ethanedioic Acid and its Salts This question covers the formation of polyesters from ethanedioic acid and propane-1,3-diol, including structural repetition. It explores biodegradability of polymers, calculation of concentrations using redox titrations involving sodium ethanedioate and potassium manganate(VII), correct use of lab glassware, and health and safety precautions. Finally, students must explain, using entropy and enthalpy changes, why ligand substitution reactions involving ethanedioate ions are thermodynamically favourable.
Organic Chemistry · Inorganic Chemistry · Physical Chemistry · 3.3.12 Polymers · 3.2.5 Transition Metals · 3.1.8 Thermodynamics · 3.1.2 Amount of Substance
- Question 2 4 marks
Chromatography of Amino Acids This question assesses students' understanding of thin-layer chromatography (TLC) in identifying amino acids. It involves calculating an Rf value to identify an unknown amino acid using provided chromatogram data and reference values. Students must also explain how to visualise amino acids after chromatography and describe why amino acids have different Rf values based on their interactions with the stationary and mobile phases.
Required Practicals · Organic Chemistry · Required Practical 12: Separation and purification techniques · 3.3.13 Amino Acids, Proteins and DNA
- Question 3 11 marks
Identification and Reactions of Ketones This question focuses on methods to identify and purify crystalline derivatives of ketones, including steps like filtration, recrystallisation, and melting point determination. It also explores the reaction of propanone with hydrogen cyanide (HCN) or potassium cyanide (KCN), assessing hazards, safety, and mechanistic understanding of nucleophilic addition reactions.
Organic Chemistry · 3.3.8 Aldehydes and Ketones
- Question 4 7 marks
Group 7 Chemistry and Halide Ion Testing This question covers reactions and tests involving halide ions, focusing on reactions of sodium bromide with sulfuric acid and the identification of halide ions using silver nitrate and ammonia. It assesses understanding of displacement reactions, colour changes, ionic equations, and the rationale for using specific reagents in qualitative analysis.
Inorganic Chemistry · Required Practicals · 3.1.7 Oxidation, Reduction, and Redox Equations · 3.2.3 Group 7(17), the Halogens · Required Practical 4: Carry out simple test-tube reactions to identify Cations and Anions
- Question 6 13 marks
Oxidation of Propan-1-ol and Yield of Propanoic Acid This question tests understanding of safe practical setup, correct reagents, and techniques involved in oxidising a primary alcohol (propan-1-ol) to a carboxylic acid (propanoic acid). It covers evaluating and correcting experimental apparatus, calculating percentage yield from mass data, and applying a test to distinguish alcohols from acids using observable results.
Required Practicals · Organic Chemistry · Required Practical 5: Distillation of a product from a reaction · 3.3.5 Alcohols
- Question 7 1 mark
Ultraviolet and Visible Light Absorption Contexts This multiple-choice question asks students to identify which of four processes does not involve absorption of UV or visible light.
Physical Chemistry · 3.1.1 Atomic Structure
- Question 9 1 mark
Mole Fraction Calculation in a Binary Solution This multiple-choice question tests understanding of mole fraction calculations. It requires interpreting a binary mixture composed of a known mass of solute and solvent, converting masses to moles using relative molecular masses, and calculating the mole fraction of one component using the appropriate formula.
Physical Chemistry · 3.1.2 Amount of Substance
- Question 10 1 mark
Electron Configuration and Noble Gases This multiple-choice question tests understanding of electron configurations and how ions can achieve noble gas configurations. Students must identify which ion has a complete outer shell equivalent to that of a noble gas.
Physical Chemistry · 3.1.1 Atomic Structure
- Question 11 1 mark
Spectroscopic and Structural Evidence for an Unknown Ester This multiple-choice question tests understanding of spectroscopic techniques and elemental analysis. Students must interpret ^1H NMR, ^13C NMR, and infrared data, along with percentage composition by mass, to assess whether the evidence supports a proposed ester structure. It challenges the ability to cross-reference empirical data with molecular structure.
Organic Chemistry · 3.3.15 Nuclear Magnetic Resonance Spectroscopy
- Question 12 1 mark
Inorganic Ionic Compounds – Properties and Misconceptions This multiple-choice question tests students’ understanding of general properties of ionic compounds, particularly what is always true about them. It assesses knowledge of structure (giant lattice), ion types (metal cations), and typical behaviour in solution and upon melting. It challenges students to distinguish between common trends and absolute rules.
Physical Chemistry · 3.1.3 Bonding
- Question 13 1 mark
Lone Pair on Central Atom – Molecular Structures This multiple-choice question tests students’ understanding of molecular shapes and electron pair repulsion, specifically identifying a species in which the central atom retains a lone pair of electrons. It draws upon VSEPR theory and knowledge of bonding and electron arrangements in species like CO₂, SO₂, PCl₆⁻, and SO₄²⁻.
Physical Chemistry · 3.1.3 Bonding
- Question 14 1 mark
Melting and Covalent Bonding This question tests your understanding of what happens at the molecular level when different types of substances melt. You are asked to identify which substance involves the breaking of covalent bonds during melting, rather than just intermolecular forces.
Physical Chemistry · 3.1.3 Bonding
- Question 15 1 mark
This question assesses your ability to deduce the correct compound from a given molecular formula by recognising the structure of aromatic compounds and applying knowledge of bonding and functional groups.
Physical Chemistry · 3.1.3 Bonding
- Question 16 1 mark
This question tests your understanding of molecular polarity. You are asked to identify which molecule has a permanent dipole, which depends on both electronegativity differences and molecular shape.
Physical Chemistry · 3.1.3 Bonding
- Question 17 1 mark
This question focuses on the properties of carboxylic acids and asks you to evaluate several statements about the compound (CH₃)₂CHCH₂COOH. You're expected to use your knowledge of functional groups and molecular interactions to determine which behaviour or property is accurate — such as hydrogen bonding, reactivity, optical activity, or naming conventions.
Organic Chemistry · Physical Chemistry · 3.3.9 Carboxylic Acids and Derivatives · 3.1.3 Bonding
- Question 18 1 mark
This question explores why certain chemical reactions may not occur, even if the reactants are mixed in the correct molar ratio. Specifically, it tests your understanding of activation energy in the context of a hydrogen–oxygen mixture at room temperature. You're asked to identify the main reason why water is not formed spontaneously.
Physical Chemistry · 3.1.5 Kinetics
- Question 19 1 mark
This question checks your understanding of the Maxwell–Boltzmann distribution curve, which represents how molecular energies are spread out in a gas at a certain temperature. You need to recognise key features of this curve, such as the fact that no molecules have zero energy and the curve is skewed, not symmetrical.
Physical Chemistry · 3.1.5 Kinetics
- Question 20 1 mark
This question explores the effect of a catalyst on a reversible chemical reaction. You're asked to consider how catalysts influence both the forward and reverse reaction rates, without changing thermodynamic quantities such as enthalpy change or the equilibrium constant.
Physical Chemistry · 3.1.6 Chemical Equilibria, Le Chatelier's Principle, and Kc
- Question 21 1 mark
This question checks your understanding of redox reactions and the role of transition metals. You are asked to identify which chemical equation does not involve the reduction of a transition metal—meaning the oxidation state of the metal does not decrease during the reaction. It requires knowledge of oxidation states and recognising transition metal redox changes.
Physical Chemistry · Inorganic Chemistry · 3.1.7 Oxidation, Reduction, and Redox Equations · 3.2.5 Transition Metals
- Question 22 1 mark
This question tests your understanding of the structure and bonding in different substances. It asks you to identify which substance contains delocalised electrons — electrons that are not associated with a single atom or bond but are free to move across a structure. These delocalised electrons are responsible for properties such as electrical conductivity in certain materials.
Physical Chemistry · 3.1.3 Bonding
- Question 23 1 mark
This question tests your understanding of stereoisomerism in compounds with C=C double bonds. Specifically, it focuses on E–Z isomerism, which occurs when each carbon in the double bond is bonded to two different groups. You are asked to identify the only compound that meets this condition.
Organic Chemistry · 3.3.1 Introduction to Organic Chemistry · 3.3.4 Alkenes
- Question 24 1 mark
This question assesses your understanding of intermolecular forces in polymer structures. It focuses on identifying which polymer can form hydrogen bonds between its chains, which significantly influences properties like strength and melting point. You’re expected to recognise the presence of functional groups (such as –NH or –OH) capable of hydrogen bonding in polymers.
Organic Chemistry · 3.3.12 Polymers
- Question 25 1 mark
This question checks your understanding of how molecular structure influences the amount of oxygen needed for complete combustion. You are asked to compare four organic compounds and determine which one requires the most oxygen per mole, based on the number and types of atoms present in each molecule.
Physical Chemistry · 3.1.2 Amount of Substance
- Question 26 1 mark
This question checks your ability to identify the product of an oxidation reaction using a common oxidising agent—acidified potassium dichromate(VI). You must know what type of organic product forms from different classes of alcohols (primary, secondary, tertiary) and be able to deduce the correct structure from a list of organic compounds.
Organic Chemistry · 3.3.5 Alcohols
- Question 27 1 mark
This question checks your knowledge of general formulae for different families of organic compounds. It requires you to recognise the characteristic molecular structure and number of atoms for alcohols, aldehydes, esters, and primary amines in a homologous series of non-cyclic molecules.
Organic Chemistry · 3.3.1 Introduction to Organic Chemistry
- Question 28 1 mark
This question assesses your understanding of identifying functional groups using chemical tests. It focuses on the reaction between silver nitrate and compounds containing a chlorine atom bonded to a carbonyl group. You are expected to know which functional group gives a white precipitate of silver chloride when treated with aqueous silver nitrate.
Organic Chemistry · 3.3.9 Carboxylic Acids and Derivatives
- Question 29 1 mark
This question assesses your understanding of percentage yield calculations in organic synthesis. You’re given the masses and relative molecular masses (Mr) of the reactant and product in a nitration reaction, and you must apply stoichiometric ratios and percentage yield to determine the actual mass of product formed. This tests both your grasp of mole ratios and your skill with percentage yield formulas.
Physical Chemistry · 3.1.2 Amount of Substance
- Question 30 1 mark
This question explores your understanding of organic synthesis and reaction pathways. You are asked to identify the correct intermediate compound, X, in the synthesis of propylamine from bromoethane. It requires knowledge of nucleophilic substitution reactions (to form a nitrile) and subsequent reduction (to form an amine).
Organic Chemistry · 3.3.14 Organic Synthesis
- Question 31 1 mark
This question checks your understanding of how different organic compounds react with dilute aqueous sodium hydroxide. It focuses on identifying which compound among the options is capable of undergoing hydrolysis under these conditions. Only certain functional groups will react, particularly those involving acyl groups like in acid anhydrides.
Organic Chemistry · 3.3.9 Carboxylic Acids and Derivatives
- Question 32 1 mark
This question checks your understanding of the reactions between amines and halogenoalkanes, focusing on the range of possible products from nucleophilic substitution. It challenges you to recognise the structure of primary, secondary, tertiary amines and quaternary ammonium salts, and spot when a product doesn’t fit the pattern based on the given reactants.
Organic Chemistry · 3.3.11 Amines
- Question 33 1 mark
This question tests your ability to recognise polymer structures, specifically those formed by condensation reactions between a dicarboxylic acid and a diamine. You need to identify the structure that contains the characteristic amide linkage (-CONH-) repeated along the chain, which defines a polyamide.
Organic Chemistry · 3.3.12 Polymers
- Question 34 1 mark
This question focuses on how different types of polymers respond to hydrolysis with concentrated aqueous sodium hydroxide. Most naturally occurring and condensation polymers (like polyamides, polyesters, and proteins) have bonds that can be broken by hydrolysis. However, addition polymers like poly(alkene), which consist only of carbon-carbon single bonds, are resistant and not hydrolysed under these conditions.
Organic Chemistry · 3.3.12 Polymers
- Question 35 1 mark
This question tests your understanding of zwitterions—molecules that have both a positive and a negative charge but are overall neutral. You're asked to identify which structure correctly shows a zwitterion form of an amino acid. Zwitterions typically form in aqueous solution where the amino group becomes protonated and the carboxylic acid group loses a proton.
Organic Chemistry · 3.3.13 Amino Acids, Proteins and DNA
- Question 36 1 mark
This question checks your understanding of complementary base pairing in DNA. You are asked to identify the base pair that is held together by three hydrogen bonds—this is a key feature in distinguishing cytosine–guanine pairs from adenine–thymine pairs, which only form two hydrogen bonds.
Organic Chemistry · 3.3.13 Amino Acids, Proteins and DNA