Key term
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
Bonding and Structure
- 10 subtopics
- 15 things to know
- Components 01, 02 and 03
What Bonding and Structure covers
How atoms are held together and what that does to a substance's properties: ionic and covalent bonding, electron pair repulsion and the shapes of molecules, electronegativity and polarity, and the intermolecular forces that decide melting point, solubility and conductivity.
Where it is assessed
Components 01, 02 and 03
Foundations, drawn on by both long papers and the unified paper.
Check the OCR specification ↗The 10 subtopics
Each one has its own page.
- Ionic bonding and the properties of ionic compoundsRecall questions on what an ionic bond is, the lattice, and why ionic compounds melt high, conduct only when molten or dissolved, dissolve in polar solvents and are brittle.Open →
- Covalent and coordinate bondingRecall questions on the covalent bond, how a coordinate bond differs, what an atom needs to be the donor, and reading a dot-and-cross diagram.Open →
- Lone pairs, bonding pairs and average bond enthalpyRecall questions on bonding and lone pairs, what average bond enthalpy measures, and comparing the strength of two bonds from their values.Open →
- Electron pair repulsion theory, linear and trigonal planar shapesRecall questions on the principle behind the theory, why lone pairs repel more strongly, and the bond angles of the linear and trigonal planar shapes.Open →
- Tetrahedral, pyramidal and non-linear shapes and their bond anglesRecall questions on methane, ammonia and water, and why their angles fall from 109.5° to 107° and 104.5°.Open →
- Octahedral shapes, ions, and drawing molecules in three dimensionsRecall questions on the octahedral angle, applying the theory to ions, and what a wedge, a dashed line and a straight line mean in a three-dimensional drawing.Open →
- Electronegativity, polar bonds and polar moleculesRecall questions on the definition and trends of electronegativity, when a bond is polar, and why water has an overall dipole while carbon dioxide has none.Open →
- Permanent and induced dipoles, and hydrogen bondingRecall questions on permanent and induced dipole interactions, what van der Waals covers, the conditions for hydrogen bonding, and why ice is less dense than water.Open →
- Simple molecular lattices and why they melt easilyRecall questions on the structure of a simple molecular lattice, why the intermolecular forces are weak compared with the covalent bonds, and the structures of iodine and ice.Open →
- Solubility and conductivity of simple molecular compoundsRecall questions on why these compounds dissolve in non-polar solvents but usually not in water, and why they conduct in no state.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Why are ionic compounds often soluble in polar solvents, why are they brittle, and why do they conduct electricity when molten?
Process
What is a covalent bond and a bonding pair, and why can ammonia donate to form a coordinate bond?
Numbers
What is a lone pair, what does average bond enthalpy measure, and what does a larger value indicate?
Key term
What does a smaller average bond enthalpy value indicate about the strength of a covalent bond?
Key term
What is the principle of electron pair repulsion theory, why do lone pairs repel more strongly than bonding pairs, and which repulsion is weakest?
Key term
What bond angle goes with a linear shape, what is the bond angle in a tetrahedral molecule, and what shape is methane?
Key term
What convention is used to show a bond lying in the plane of the paper in a 3-D representation?
Process
What is electronegativity, and how does it change across a period and up a group?
Process
What conditions produce a polar bond, how does a permanent dipole arise, and what is a polar molecule?
Numbers
What two factors decide whether a molecule is polar, and why does water have a dipole while carbon dioxide does not?
Key term
What is a simple molecular lattice?
Process
What happens to the covalent bonds when a simple molecular substance melts, and what structures do iodine and ice have?
Key term
What are the shapes of a water molecule and an ammonia molecule, and what bond angle is found in an octahedral molecule?
Process
Why are simple molecular compounds generally insoluble in water, why do stronger intermolecular forces give higher boiling points, and what does the higher boiling point of two compounds indicate?
Take Bonding and Structure further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Ionic bond vs Covalent bond
Ionic bond: strong electrostatic attraction between oppositely charged ions. Covalent bond: electrostatic attraction between shared electrons and both nuclei.
Bonding pair vs Lone pair
Bonding pair: two shared electrons forming a covalent link. Lone pair: two outer-shell electrons not used in bonding.
Permanent dipole vs Instantaneous dipole
Permanent dipole: a lasting separation of partial charge within a bond or molecule. Instantaneous dipole: a temporary charge separation caused by electron movement.
Questions from this topic
Each one with the model answer underneath.
- 1
What is an ionic bond?
Model answer
The strong electrostatic attraction between oppositely charged ions
- 2
What type of force holds ions together in an ionic lattice?
Model answer
Strong electrostatic attraction
- 3
Describe the structure of ionic compounds.
Model answer
Giant ionic lattice structures with ions arranged in a regular repeating three-dimensional pattern
- 4
Why do ionic compounds have high melting and boiling points?
Model answer
A large amount of energy is required to overcome the strong electrostatic attractions between ions throughout the lattice
- 5
Why do solid ionic compounds not conduct electricity?
Model answer
The ions are held in fixed positions within the lattice and cannot move
- 6
In what physical states can ionic compounds conduct electricity, and why not in the solid state?
Model answer
Molten or dissolved in water, because ions are free to move; in the solid state ions are fixed in position and cannot carry charge
What is inside Levo
Six ways to work the same material.
Bonding and Structure revision questions
- What does Bonding and Structure cover in OCR A-Level Chemistry?
- 10 subtopics: ionic bonding and the properties of ionic compounds, covalent and coordinate bonding, lone pairs, bonding pairs and average bond enthalpy, electron pair repulsion theory, linear and trigonal planar shapes, tetrahedral, pyramidal and non-linear shapes and their bond angles, octahedral shapes, ions, and drawing molecules in three dimensions, electronegativity, polar bonds and polar molecules, permanent and induced dipoles, and hydrogen bonding, simple molecular lattices and why they melt easily and solubility and conductivity of simple molecular compounds. Each one has its own page with questions and model answers.
- How is Bonding and Structure organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Bonding and Structure, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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