Numbers
OCR A-Level Chemistry H432
Foundations in Chemistry
Topic overviewAtomic structure, isotopes and counting sub-atomic particlesRelative isotopic, atomic, molecular and formula massPredicting ionic charges and the common ionsWriting formulae, balanced equations and ionic equationsThe mole, molar mass and the Avogadro constantEmpirical and molecular formulae, and hydrated saltsGas volumes, concentration and the ideal gas equationStoichiometry, percentage yield and atom economyApparatus, and why high atom economy mattersMathematical skills and measuring mass, volume and gasAcids, alkalis, dissociation and neutralisationPreparing a standard solutionCarrying out a titration and its calculationsPlanning an experiment: variables, apparatus and recording resultsPractical safety, heating and filtrationUncertainty, percentage error, precision and accuracyEvaluating results: anomalies, conclusions, limitations and improvementsAssigning oxidation numbersRoman numerals in names, and the chlorate and nitrate ionsOxidation, reduction and metals reacting with acidsRedox equations and identifying what is oxidisedShells, orbitals and sub-shellsThe order in which sub-shells fillWriting electron configurations for atoms and ions
Bonding and Structure
Topic overviewIonic bonding and the properties of ionic compoundsCovalent and coordinate bondingLone pairs, bonding pairs and average bond enthalpyElectron pair repulsion theory, linear and trigonal planar shapesTetrahedral, pyramidal and non-linear shapes and their bond anglesOctahedral shapes, ions, and drawing molecules in three dimensionsElectronegativity, polar bonds and polar moleculesPermanent and induced dipoles, and hydrogen bondingSimple molecular lattices and why they melt easilySolubility and conductivity of simple molecular compounds
Periodic Table and Energy
Topic overviewPeriodicity and the electron configurations of periods 2 and 3The blocks, and first and successive ionisation energiesMetallic and giant covalent structures and their propertiesGroup 2 reactions with oxygen, water and acidsIonisation energy down Group 2 and the alkalinity of the hydroxidesUses of Group 2 compounds in agriculture and medicineThe halogens: boiling points, London forces and reactivityHalogen displacement reactions and the colours seenDisproportionation and the chlorination of waterTesting for halide ions with silver nitrate and ammoniaTesting for carbonate, sulfate and halide ionsTesting for ammonium ions and the order of the testsConcentration, pressure and measuring reaction rateCatalysts and their industrial importanceThe Boltzmann distribution, temperature and catalysts
Enthalpy Changes
Topic overviewExothermic and endothermic reactions and enthalpy profilesStandard conditions and the standard enthalpy changesBond enthalpies, q = mcΔT and calorimetryCalculating enthalpy change from bond enthalpiesWhy average bond enthalpies give only an approximationHess' law and enthalpy cycles from combustion and formation dataWorking through an enthalpy cycle and the sign conventionsCalorimetry and correcting for heat loss
Chemical Equilibrium
Basic Concepts of Organic Chemistry
Topic overviewIUPAC nomenclature and the alkyl groupsGeneral, structural, displayed and skeletal formulaeHomologous series, functional groups and saturationStructural isomers, bond fission and curly arrowsChain, position and functional group isomerismCurly arrows, homolytic and heterolytic fissionNucleophiles, electrophiles, radicals and the mechanism steps
Core Organic Chemistry
Topic overviewAlkanes: bonding, shape and boiling pointsCombustion of alkanes and their reaction with halogensThe radical substitution mechanism and its limitationsAlcohols: polarity, solubility and classificationOxidation, dehydration and substitution reactions of alcoholsHydrolysis of haloalkanes and comparing the ratesNucleophilic substitution and carbon-halogen bond strengthCFCs, radicals and the catalytic destruction of ozoneCombining analytical techniques to identify a compound
Alkenes
Topic overviewAlkenes: the double bond, sigma and pi bonding, and shapeE/Z and cis-trans isomerism in alkenesHydrogenation, halogenation and hydration of alkenesElectrophilic addition, carbocation stability and Markownikoff's ruleAddition polymerisation and repeat unitsWaste polymers, and biodegradable and photodegradable alternatives
Organic Synthesis
How Fast?
Topic overviewRate equations, order and the rate constantDeducing orders and finding the units of kWhat the rate equation reveals about the mechanismConcentration-time graphs and continuous monitoringHalf-life and the rate constant of a first-order reactionRate-concentration graphs and the initial rates methodClock reactions, colorimetry and analysing kinetic graphsThe rate-determining step and testing a proposed mechanismTemperature, the rate constant and the Arrhenius equationThe ln k against 1/T graph and finding the activation energy
Physical Chemistry and Transition Elements
Topic overviewMole fraction, partial pressure and ICE tablesKc and Kp expressions, their units and calculationsWhat changes the equilibrium constant, and the reaction quotientLattice enthalpy and the Born-Haber cycleEnthalpy of solution and hydration, and the effect of ionic charge and sizeEntropy and calculating entropy changeGibbs free energy and thermodynamic feasibility
Acids, Bases and Buffers
Topic overviewBrønsted-Lowry acids and bases and their reactionsKa, pKa, pH and the ionic product of waterCalculating the pH of strong acids, strong bases and weak acidspH and hydrogen ion concentrationWhat a buffer is and how it resists a change in pHBuffer calculations and the buffer that controls blood pHTitration curves, choosing an indicator and using a pH meterpH titration curves for the four acid-base combinationsHow an indicator works and choosing the right one
Redox and Electrode Potentials
Topic overviewOxidising and reducing agents, and balancing half-equationsCombining half-equations and using oxidation numbersRedox titrations and their calculationsStandard electrode potentials and setting up half-cellsThe electrochemical series and predicting feasibilityStorage cells and fuel cells
Transition Elements
Topic overviewLigands, complex ions and coordination numberElectron configurations from Sc to Zn, and which are transition elementsVariable oxidation states, coloured ions and catalysisThe shapes of complexes, stereoisomerism and cisplatinLigand substitution, haemoglobin and the copper complexesHydroxide precipitates of iron, manganese and chromiumRedox interconversions of iron, chromium and copperWhy ligand substitution happens and the changes it causesPrecipitation reactions written as aqua complexesDissolving hydroxides in excess ammonia and distinguishing the ions
Aromatic Compounds
Topic overviewThe delocalised model of benzene and the evidence for itNitration, halogenation and Friedel-Crafts reactions of benzeneThe reactions of phenol, and directing effectsElectrophilic substitution and directing effectsPhenol: acidity, bromination and nitrationWhy phenol is more reactive than benzene, and planning a synthesis
Organic Chemistry and Analysis
Topic overviewOxidation and reduction of carbonyls, and the addition of HCNThe nucleophilic addition mechanism2,4-DNPH and Tollens' reagentCarboxylic acids: solubility and reactions with metals, carbonates and basesEsterification and the hydrolysis of estersAcyl chlorides and their reactions with alcohols, amines and ammoniaAmines as bases, and preparing aliphatic aminesSecondary and tertiary amines, and preparing aromatic aminesAmino acids, their reactions, and amidesOptical isomerism and identifying a chiral centreCondensation polymerisation and the ester and amide linkagesHydrolysing condensation polymers and telling them from addition polymersNitriles from haloalkanes and from carbonyl compoundsFriedel-Crafts reactions and lengthening the carbon chainThin-layer and gas chromatography, Rf values and retention timesTest-tube tests for the organic functional groupsTests for the inorganic ions and interpreting chromatograms
Spectroscopy
Topic overviewCarbon-13 and proton NMR: peaks, chemical shift and integrationSpin-spin splitting and predicting a spectrumTMS, deuterated solvents and the D₂O shakeCombining elemental analysis, mass spectrometry, IR and NMRMolecular formula from the molecular ion, and fragmentation lossesWhat IR and NMR each contribute to a structureInfrared absorption, global warming and breathalysersA systematic approach and the degree of unsaturation
Physical Chemistry and Transition Elements
- 7 subtopics
- 18 things to know
- Components 01 and 03
What Physical Chemistry and Transition Elements covers
The quantitative treatment of equilibrium with Kc and Kp, lattice enthalpy through the Born-Haber cycle and the enthalpies of solution and hydration, and entropy and Gibbs free energy as the test of whether a reaction is feasible.
Where it is assessed
Components 01 and 03
Periodic Table, Elements and Physical Chemistry, then the unified paper.
Check the OCR specification ↗The 7 subtopics
Each one has its own page.
- Mole fraction, partial pressure and ICE tablesRecall questions on mole fraction and partial pressure, Dalton's law, and using an ICE table to reach the equilibrium amounts.Open →
- Kc and Kp expressions, their units and calculationsRecall questions on writing each expression, homogeneous against heterogeneous equilibria, why solids and pure liquids are omitted, and deriving the units.Open →
- What changes the equilibrium constant, and the reaction quotientRecall questions on why only temperature changes K, what concentration, pressure and a catalyst do instead, and predicting the shift from Q against K.Open →
- Lattice enthalpy and the Born-Haber cycleRecall questions on the definition and sign of lattice enthalpy, the atomisation, ionisation and electron affinity terms, and the relationship around the cycle.Open →
- Enthalpy of solution and hydration, and the effect of ionic charge and sizeRecall questions on the three linked terms, why dissolving can be endothermic, and how ionic charge and radius affect both lattice and hydration enthalpies.Open →
- Entropy and calculating entropy changeRecall questions on what entropy measures, the order of the three states, what a change in the number of gas molecules does, and calculating ΔS from standard entropies.Open →
- Gibbs free energy and thermodynamic feasibilityRecall questions on ΔG = ΔH − TΔS, the condition for feasibility, and why a negative ΔG does not guarantee that a reaction is observed.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
In an ICE table, how are the changes in amount and the equilibrium moles worked out, and what is Kc?
Key term
What is Kp, and what defines a homogeneous and a heterogeneous equilibrium?
Numbers
How does raising the temperature change the equilibrium constant of an endothermic reaction, and why, and does changing concentration change the equilibrium constant?
Key term
Does adding a catalyst change the value of the equilibrium constant?
Key term
If the reaction quotient Q is greater than the equilibrium constant K, in which direction will the system shift?
Key term
What does a small value of the equilibrium constant K indicate about the position of equilibrium?
Process
What is lattice enthalpy, is it exothermic or endothermic, and what does its magnitude tell you?
Process
What are the enthalpy changes of formation and of atomisation, and what does the metal's atomisation term represent?
Numbers
What do the electron affinities represent in a Born-Haber cycle, and which principle does the cycle apply?
Numbers
How is lattice enthalpy calculated from a Born-Haber cycle, and what are the enthalpy changes of solution and of hydration?
Process
Explain why smaller ions produce more exothermic lattice enthalpies.
Numbers
Why do smaller ions have more exothermic enthalpies of hydration?
Process
How do the three states of matter rank for entropy, why does a gas have more entropy than a liquid, and what happens when a reaction makes more gas molecules?
Numbers
Why does the decomposition of calcium carbonate raise the entropy, what happens when a reaction reduces the number of gas molecules, and how is ΔS calculated from standard entropies?
Numbers
What does T represent in ΔG = ΔH − TΔS, what is ΔG when ΔH = +281 kJ mol⁻¹, T = 891 K and ΔS = +74 J K⁻¹ mol⁻¹, and what must ΔG be for a feasible process?
Key term
What kinetic factor can prevent a thermodynamically feasible reaction from occurring?
Numbers
State the Gibbs free-energy equation.
Take Physical Chemistry and Transition Elements further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Enthalpy change vs Entropy change
Enthalpy change: heat energy transferred under constant pressure. Entropy change: change in dispersal of energy and particles.
Enthalpy of hydration vs Enthalpy of solution
Enthalpy of hydration: the enthalpy change when gaseous ions become aqueous ions. Enthalpy of solution: the enthalpy change when one mole of ionic solid dissolves in water.
Lattice formation enthalpy vs Lattice dissociation enthalpy
Lattice formation enthalpy: the enthalpy change when gaseous ions form one mole of ionic solid. Lattice dissociation enthalpy: the enthalpy change when one mole of ionic solid separates into gaseous ions.
Questions from this topic
Each one with the model answer underneath.
- 1
Define mole fraction.
Model answer
Mole fraction is the ratio of the number of moles of one component to the total number of moles of all components in a mixture.
- 2
State the formula for calculating mole fraction and define each term.
Model answer
xₐ = nₐ / n_total, where xₐ is the mole fraction of component A, nₐ is the number of moles of component A, and n_total is the total number of moles of all components.
- 3
Calculate the mole fraction when moles of component A = 2.9 mol, total moles = 4.1 mol.
Model answer
Mole fraction = 2.9 ÷ 4.1 = 0.71.
- 4
Define partial pressure of a gas in a mixture.
Model answer
Partial pressure is the pressure that a gas in a mixture would exert if it alone occupied the total volume at the same temperature.
- 5
State the relationship between partial pressure, mole fraction, and total pressure.
Model answer
Partial pressure equals mole fraction multiplied by total pressure: pₐ = xₐ × P_total.
- 6
How are partial pressures obtained before substituting into a Kp expression?
Model answer
Calculate partial pressures from mole fractions and total pressure using pₐ = xₐ × P_total.
What is inside Levo
Six ways to work the same material.
Physical Chemistry and Transition Elements revision questions
- What does Physical Chemistry and Transition Elements cover in OCR A-Level Chemistry?
- 7 subtopics: mole fraction, partial pressure and ice tables, kc and kp expressions, their units and calculations, what changes the equilibrium constant, and the reaction quotient, lattice enthalpy and the born-haber cycle, enthalpy of solution and hydration, and the effect of ionic charge and size, entropy and calculating entropy change and gibbs free energy and thermodynamic feasibility. Each one has its own page with questions and model answers.
- How is Physical Chemistry and Transition Elements organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Physical Chemistry and Transition Elements, on a schedule.
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