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A-LevelAQA
Chemistry
Exam Questions
Protons, neutrons and electrons: relative charge and relative massNewIsotopes and why they existNewWriting nuclide notation and working out numbers of subatomic particlesNewMeaning of relative atomic mass (Ar) and relative isotopic massNewCalculating Ar from isotopic abundance dataNewMass spectrometer basics: vaporisation, ionisation, acceleration, detectionNewInterpreting mass spectra: m/z peaks, molecular ion peakNewElectron shells and subshells (s, p, d) as energy levelsNewOrbitals as regions of electron probabilityNewElectron configurations for atoms and ions (including exceptions)NewFirst ionisation energy: definition and unitsNewTrends in first ionisation energy across a periodNewSuccessive ionisation energies and what they reveal about shellsNewExplaining IE anomalies: subshells, shielding, electron pairingNew
The mole as Avogadro’s number of particlesNewConverting between moles, mass and molar massNewEmpirical formula from percentage compositionNewMolecular formula from empirical formula and MrNewWriting balanced equations for calculationsNewUsing stoichiometric ratios to calculate reacting massesNewLimiting reagent problemsNewCalculating theoretical yieldNewPercentage yield calculationsNewAtom economy and why it matters (efficiency and waste)NewConcentration in mol dm⁻³ and converting volume units (cm³ ↔ dm³)NewUsing c = n/V for solution calculationsNewGas volume at RTP (24.0 dm³ mol⁻¹): when it appliesNewTitration calculations: mean titre and moles at equivalenceNew
Ionic bonding as electrostatic attraction in a latticeNewCovalent bonding as shared pairs of electronsNewDative (coordinate) bonding: what it is and how to draw itNewMetallic bonding: positive ions in a sea of delocalised electronsNewElectronegativity and what affects itNewBond polarity and dipoles from electronegativity differencesNewIntermolecular forces: London, permanent dipole-dipole, hydrogen bondingNewComparing intermolecular forces using boiling point dataNewShapes of molecules and ions using electron pair repulsion (VSEPR)NewBond angles: predicting and explaining deviationsNewMeaning of oxidation state and how to calculate itNewIonic lattices vs molecular vs giant covalent vs metallic structuresNewLinking structure and bonding to melting point, conductivity, solubilityNew
Endothermic vs exothermic reactions (energy profile diagrams)NewEnthalpy change (ΔH) and standard conditionsNewStandard enthalpy of combustion: definition and conventionsNewStandard enthalpy of formation: definition and conventionsNewUsing q = mcΔT in calorimetry calculationsNewConverting heat change to molar enthalpy changeNewCalorimetry errors and improvements: heat loss, incomplete combustion, insulationNewHess’s law as an energy cycle principleNewHess cycles using formation enthalpiesNewHess cycles using combustion enthalpiesNewMean bond enthalpy: meaning and limitationsNewCalculating ΔH from mean bond enthalpiesNewExplaining differences between bond enthalpy and Hess resultsNew
What rate of reaction means (change in concentration per unit time)NewCollision theory: successful collisions and activation energyNewEnergy profile diagrams for activation energyNewMaxwell–Boltzmann distribution: what the curve showsNewTemperature changes and Maxwell–Boltzmann explanation for rate increaseNewConcentration changes and collision frequencyNewPressure changes for gases and collision frequencyNewCatalysts: alternative pathway and lower activation energyNewMaxwell–Boltzmann explanation for catalysis (more particles above Ea)NewMeasuring rate using gas volume or mass loss methodsNewInterpreting concentration–time graphs and tangent gradientsNewChoosing a suitable method for a given reaction (practical constraints)New
Dynamic equilibrium: forward and reverse rates equalNewWriting equilibrium expressions for KcNewUnits of Kc and when they matterNewCalculating Kc from equilibrium concentrationsNewUsing ICE tables to find equilibrium amountsNewHomogeneous vs heterogeneous equilibria (what appears in Kc)NewLe Chatelier: concentration changes and direction of shiftNewLe Chatelier: temperature changes and direction of shift (link to ΔH)NewLe Chatelier: pressure changes (gases only, moles of gas comparison)NewCatalysts and equilibrium position (what changes and what doesn’t)NewInterpreting equilibrium graphs (concentration vs time)NewUsing Kc magnitude to comment on position of equilibriumNew
Oxidation and reduction in terms of oxidation statesNewOxidation and reduction in terms of electron transferNewAssigning oxidation states in molecules and ionsNewIdentifying oxidising agents and reducing agentsNewWriting half-equations for redox changesNewBalancing redox equations in acidic conditionsNewDisproportionation: recognising and explaining itNewRedox titration ideas (what the endpoint means)NewLinking redox to real systems (corrosion, bleaching, batteries)New
Lattice enthalpy: formation vs dissociation definitionsNewBorn–Haber cycles: why we use themNewConstructing a Born–Haber cycle from given dataNewCalculating lattice enthalpy using a Born–Haber cycleNewFactors affecting lattice enthalpy (ionic charge and radius)NewEntropy (ΔS) as disorder and energy dispersalNewPredicting sign of ΔS from state changes and moles of gasNewGibbs free energy (ΔG) and feasibilityNewUsing ΔG = ΔH − TΔS for feasibility at a given temperatureNewTemperature dependence of feasibility (when reactions become feasible)NewLinking ΔG to equilibrium ideas (conceptual link)New
Rate equation form: rate = k[A]^m[B]^nNewOrders of reaction: meaning of 0th, 1st and 2nd orderNewDetermining order from initial rate dataNewUsing rate equations to calculate kNewUnits of k from overall orderNewHow rate data can suggest steps in a mechanismNewArrhenius equation as a temperature–k relationshipNewUsing Arrhenius graphs (ln k vs 1/T) to find EaNewActivation energy from experimental rate constantsNewChoosing a plausible rate-determining step from ordersNewComparing catalysts using activation energy and rate dataNew
When to use Kp instead of Kc (gases)NewPartial pressure and how to calculate itNewWriting Kp expressions using partial pressuresNewUnits of Kp and what they depend onNewCalculating Kp from equilibrium partial pressuresNewUsing total pressure + mole fractions to find partial pressuresNewLinking Kp magnitude to equilibrium positionNewHow temperature affects Kp (via ΔH and equilibrium shift)New
Redox as electrode processes in cellsNewStandard electrode potential: what it representsNewStandard hydrogen electrode as a referenceNewWriting half-equations using IUPAC conventionsNewCell diagrams and conventional cell representationNewCalculating Ecell from standard electrode potentialsNewPredicting feasibility using Ecell (spontaneous vs non-spontaneous)NewIdentifying which electrode is oxidation/reductionNewNon-standard conditions: why conditions matter (conceptual, no Nernst)NewRechargeable vs non-rechargeable cells: what reversible meansNewFuel cells: hydrogen fuel cell electrode reactions (concept level)NewCommercial cells example (lithium cell) and what happens at each electrodeNew
Brønsted–Lowry acids and bases: proton transferNewConjugate acid–base pairsNewStrong vs weak acids: what fully dissociated meansNewpH as a logarithmic measure: pH = −log10[H+]NewConverting between pH and [H+]NewCalculating pH of a strong acid from concentrationNewIonic product of water Kw and what it meansNewUsing Kw to find pH of strong basesNewKa for weak acids: what it representsNewCalculating pH of weak acids using Ka (approximation where valid)NewBuffer solutions: what they are and why they resist pH changeNewCalculating pH of acidic buffers (Ka + concentrations)NewTitration curves: strong/weak acid–base combinations and key featuresNew
Classifying elements as s, p, d and f blockNewPeriod 3 atomic radius trend: explanationNewPeriod 3 first ionisation energy trend: explanation (including anomalies)NewPeriod 3 melting point trend: structure and bonding explanationsNewMetallic → giant covalent → molecular transitions across Period 3NewOxides across Period 3: linking structure to properties (overview)NewUsing data tables to justify periodic trends in exam answersNewComparing explanations: shielding, nuclear charge, electron configurationNew
Group 2 physical trends: atomic radius and first ionisation energyNewGroup 2 melting points: structure and bonding explanationNewReactions with water: observations and equations (Mg → Ba)NewHydroxides: solubility trend and pH implicationsNewSulfates: solubility trend and applicationsNewThermal stability of carbonates and nitrates (trend + explanation)NewUses of Group 2 compounds in medicine and agricultureNewMagnesium in the extraction of titanium (why Mg works)New
Halogen electronegativity trend and implicationsNewHalogen boiling point trend: London forces explanationNewOxidising ability trend down Group 7NewHalogen displacement reactions in aqueous solutionNewHalide ions as reducing agents: trend and reasoningNewChlorine with water: formation of Cl− and ClO− (equation and meaning)NewChlorine in water treatment: benefits and risks (balanced judgement)NewHalide tests with silver nitrate and ammonia (observations + equations)New
Reactions of sodium and magnesium with water: comparing behaviourNewOxides across Period 3: basic to acidic trendNewOxides reacting with water: predicting pH of resulting solutionsNewAluminium oxide as amphoteric: reactions with acids and basesNewChlorides across Period 3: ionic vs covalent characterNewHydrolysis of chlorides (eg AlCl3, PCl5) and pH effectsNewExplaining trends using electronegativity and polarisationNewWriting equations for key oxide and chloride reactionsNew
What makes a transition metal (incomplete d subshell in ions)NewComplex ions: central metal ion + ligandsNewLigands as lone pair donors (coordinate bonding)NewSubstitution reactions: ligand exchange with H2O, NH3, Cl−NewShapes of complexes: octahedral vs tetrahedralNewCis–trans isomerism in octahedral complexesNewOptical isomerism with bidentate ligands (concept and drawings)NewWhy transition metal compounds are coloured (d–d transitions)NewFactors changing colour: oxidation state, ligand, coordination numberNewColorimetry: absorbance to find concentration (calibration curve)NewVariable oxidation states: vanadium redox changes in solutionNewTransition metals as catalysts: heterogeneous vs homogeneousNewCatalyst supports: surface area and cost argumentsNew
Precipitation reactions as ionic tests (what a precipitate shows)NewTesting cations: Group 2 hydroxide precipitates (observations)NewTesting ammonium ions with NaOH and warming (ammonia test)NewTesting halide ions with AgNO3 and NH3 (confirmatory tests)NewTesting carbonate ions (CO2 test with acid + limewater)NewTesting sulfate ions (Ba2+ test and insoluble BaSO4)NewUsing ionic equations for precipitation testsNewUsing observations to identify unknown ions (structured approach)NewAvoiding test interference and improving reliability (washing, controls)New
Different ways to represent organic compounds (empirical → skeletal)NewHomologous series and functional groupsNewNaming alkanes, alkenes, halogenoalkanes, alcohols (IUPAC basics)NewStructural isomerism: chain, position and functional group isomersNewReaction mechanisms: why we use curly arrowsNewHeterolytic vs homolytic bond fissionNewElectrophiles and nucleophiles: recognising and describing themNewFree-radical substitution: overview and key featuresNewNucleophilic substitution: overview and key featuresNewElectrophilic addition: overview and key featuresNewOxidation reactions in organic chemistry (overview)NewLinks: conditions, reagents and functional group changeNew
Alkanes as saturated hydrocarbons and general formulaNewTrends in boiling point with chain length (London forces)NewFractional distillation of crude oil (principle and fractions)NewCracking: why it’s needed and what it producesNewCatalytic cracking vs steam cracking (conditions and products)NewCombustion of alkanes: complete vs incompleteNewCarbon monoxide and soot: conditions and hazardsNewFree-radical substitution with halogens: overall reactionNewInitiation, propagation and termination stepsNewExplaining product mixtures in radical substitutionNewWriting mechanisms with curly arrows (radical fishhooks)NewOzone depletion and CFCs: radical chain reactions (conceptual)New
Naming halogenoalkanes (primary, secondary, tertiary)NewCarbon–halogen bond polarity and its consequencesNewNucleophilic substitution with OH− to form alcoholsNewNucleophilic substitution with CN− to form nitriles (chain lengthening)NewNucleophilic substitution with NH3 to form amines (introduction)NewComparing rates: iodo > bromo > chloro (bond enthalpy)NewPrimary vs tertiary: mechanism choice (SN2 vs SN1 idea level)NewHydrolysis practical: ethanol and heating under refluxNewElimination to form alkenes (conditions and competing reactions)NewEquations for substitution and eliminationNewUsing IR to spot halogenoalkane functional features (link lesson)New
Alkenes as unsaturated hydrocarbons and general formulaNewE/Z isomerism: why restricted rotation mattersNewAssigning E and Z using CIP priority rules (step-by-step)NewElectrophilic addition: how the double bond reactsNewReaction with Br2: bromine water test and mechanism ideaNewReaction with HX (eg HBr): products and mechanism ideaNewMarkovnikov’s rule: predicting the major product (where relevant)NewAddition polymerisation: turning alkenes into polymersNewConditions for polymerisation (general)NewComparing addition vs condensation polymerisation (preview)NewUsing alkenes as chemical feedstocks (context lesson)New
Naming alcohols and classifying as primary/secondary/tertiaryNewAlcohol intermolecular forces and boiling point trendsNewEthanol production by fermentation: conditions and limitationsNewEthanol production by hydration of ethene: conditions and catalystsNewComparing fermentation vs hydration (rate, purity, sustainability)NewOxidation of primary alcohols to aldehydes (conditions)NewOxidation of primary alcohols to carboxylic acids (conditions)NewOxidation of secondary alcohols to ketones (conditions)NewWhy tertiary alcohols resist oxidation (structure explanation)NewDehydration of alcohols to alkenes (elimination conditions)NewSubstitution of alcohols to halogenoalkanes (overview)NewChoosing reagents and conditions from functional group targetsNew
Combustion analysis: CO2 and H2O data to find empirical formulaNewMass spectrometry: molecular ion and fragmentationNewInterpreting mass spectra for simple organic fragmentsNewInfrared (IR) spectroscopy: what bonds absorb IR and whyNewRecognising key IR absorptions (O–H, C=O, C–H, N–H)NewUsing IR to distinguish functional groups in unknownsNewUsing multiple techniques together (MS + IR + chemical tests)NewWriting a logical identification sequence for exam questionsNew
What makes a chiral centre (four different groups)NewEnantiomers as non-superimposable mirror imagesNewDrawing 3D representations (wedge/dash)NewOptical activity and plane-polarised lightNewRacemic mixtures and why they’re optically inactive overallNewBiological significance of enantiomers (drugs and receptors)NewDistinguishing enantiomers, structural isomers, E/Z isomersNewExam technique: spotting chirality quickly in skeletal structuresNew
Naming aldehydes and ketonesNewCarbonyl group: polarity and nucleophilic addition (overview)NewOxidation of alcohols revisited (making aldehydes/ketones)NewTollens’ test for aldehydes: observations and explanationNewFehling’s/Benedict’s test: observations and explanationNewWhy ketones don’t react in these oxidation testsNewReduction of carbonyls to alcohols (NaBH4 / LiAlH4 idea level)New2,4-DNP test for carbonyls: observations and purposeNewDistinguishing aldehydes, ketones and alcohols using testsNew
Naming carboxylic acids and recognising acidity trendsNewCarboxylic acid strength vs alcohols/phenols (comparison lesson)NewReactions with carbonates: CO2 test and equationsNewEsterification: making esters from acids and alcohols (conditions)NewEster hydrolysis: acidic vs alkaline hydrolysis (differences)NewAcyl chlorides: why they are reactive (bond polarity)NewAcyl chloride reactions with water, alcohols and ammoniaNewAmides: formation from acyl chlorides and amines/ammoniaNewComparing reactivity: acyl chlorides vs esters vs carboxylic acidsNew
Benzene structure: delocalised π system and stabilityNewEvidence for benzene’s structure (bond lengths and enthalpy ideas)NewWhy benzene undergoes substitution not additionNewElectrophilic substitution: general mechanism outlineNewNitration of benzene: reagents, conditions and mechanism stepsNewHalogenation of benzene: catalyst role (AlCl3 / FeBr3)NewFriedel–Crafts acylation/alkylation (overview, catalysts)NewDirecting effects with substituents (basic overview if taught)NewUsing aromatic chemistry to build synthesis routesNew
Naming amines and classifying as primary/secondary/tertiaryNewAmines as bases: lone pair acceptance and pH effectsNewComparing basicity: aliphatic amines, ammonia, aromatic aminesNewMaking amines: reduction of nitriles (overview)NewFormation of amides from acyl chlorides + amines (link lesson)NewDiazotisation of aromatic amines (phenylamine): conditions (overview)NewAzo dyes: coupling reactions and coloured products (overview)NewSalt formation with acids: making ammonium saltsNewTest-tube observations suggesting an amine functional groupNew
Addition polymerisation: repeating units from alkene monomersNewDrawing repeating units correctly from monomersNewPoly(alkenes) properties: chain length, branching, intermolecular forcesNewCondensation polymerisation: polymers + small molecule by-productNewPolyesters: formation from diols and dicarboxylic acidsNewPolyamides: formation from diamines and dicarboxylic acids/acyl chloridesNewIdentifying monomers from a polymer repeat unitNewPolymer disposal: recycling, biodegradability, incineration (balanced view)NewBiopolymers and sustainability (context lesson)New
Amino acids as zwitterions: internal acid–base behaviourNewIsoelectric point and why charge changes with pHNewPeptide bond formation: condensation between amino acidsNewHydrolysis of peptides and proteins (acid/base/enzyme overview)NewProtein structure levels: primary → quaternary (concept lesson)NewHydrogen bonding and shapes in proteins (concept lesson)NewDNA components: sugar, phosphate, basesNewBase pairing and hydrogen bonding in DNANewDNA as a condensation polymer (link lesson)NewUsing chemistry to explain biological function (synoptic lesson)New
Planning a synthesis: choosing functional group interconversionsNewWriting multi-step routes with correct reagents and conditionsNewHalogenoalkanes as starting points (substitution vs elimination choices)NewAlkenes as starting points (addition reactions to build complexity)NewUsing oxidation and reduction strategically in routesNewProtecting group idea (concept-level awareness where relevant)NewPurification: recrystallisation vs distillation (when to use which)NewCalculating percentage yield in multi-step synthesisNewImproving yield and purity: drying, excess reagent, separationNewUsing IR/MS/NMR evidence to confirm products in a routeNew
What NMR measures (hydrogen environments in ¹H NMR)NewChemical shift (δ) and what influences itNewShielding and deshielding: electron density effectsNewSplitting patterns: the n+1 ruleNewInterpreting integration for relative numbers of H atomsNewUsing splitting, integration, shifts to propose structuresNewCommon ¹H NMR features (alkyl, aromatic, aldehyde, acid O–H)NewCombining NMR with IR/MS to identify unknownsNew
Chromatography as separation by partition between phasesNewStationary phase vs mobile phase (what each does)NewThin-layer chromatography (TLC): setup and how to run itNewCalculating Rf values and interpreting themNewUsing TLC to assess purity and reaction progressNewGas chromatography (GC): separation by volatility and interactionsNewRetention time and what affects itNewUsing chromatography with mass spectrometry (GC-MS concept)NewChoosing the right chromatography method for a scenarioNew
Safe handling of chemicals and interpreting hazard informationNewRecording measurements correctly (mass, time, volume, temperature)NewUsing volumetric apparatus accurately (pipette, burette, volumetric flask)NewPlanning variables: independent, dependent and control variablesNewPresenting data in tables with correct headings and unitsNewGraph skills: axes, plotting points, best-fit curvesNewDetermining gradient (including tangents) and what it meansNewUncertainty, accuracy and precision: what each term meansNewIdentifying sources of systematic and random errorNewEvaluating methods and suggesting realistic improvementsNewUsing pH meters/probes and calibrating where appropriateNewMeeting CPAC expectations through consistent lab practiceNew
Make a volumetric solution and carry out a simple acid–base titrationNewMeasure an enthalpy change (calorimetry)NewInvestigate how rate changes with temperatureNewIdentify cations/anions by test-tube reactions (Group 2, NH4+, halides, OH−, CO3^2−, SO4^2−)NewDistil a product from a reactionNewTest for alcohol, aldehyde, alkene and carboxylic acid functional groupsNewMeasure rate by initial-rate method and by continuous monitoringNewMeasure the EMF of an electrochemical cellNewInvestigate pH change in weak acid–strong base and strong acid–weak base reactionsNewPrepare a pure organic solid/liquid and test purityNewIdentify transition metal ions by test-tube reactionsNewSeparate species by thin-layer chromatography (TLC)New
