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
Spectroscopy
- 8 subtopics
- 19 things to know
- Components 02 and 03
What Spectroscopy covers
Carbon-13 and proton NMR and what each feature of a spectrum tells you, and then the combination of elemental analysis, mass spectrometry, infrared and NMR that settles a structure.
Where it is assessed
Components 02 and 03
Synthesis and Analytical Techniques, then the unified paper.
Check the OCR specification ↗The 8 subtopics
Each one has its own page.
- Carbon-13 and proton NMR: peaks, chemical shift and integrationRecall questions on what the number of peaks and the chemical shift indicate in each kind of NMR, what proton decoupling means, and what integration gives.Open →
- Spin-spin splitting and predicting a spectrumRecall questions on the n + 1 rule, what a singlet, doublet, triplet and quartet each indicate, and predicting a spectrum from a structure.Open →
- TMS, deuterated solvents and the D₂O shakeRecall questions on tetramethylsilane as the NMR reference standard, deuterated solvents such as CDCl₃, and using a D₂O shake to identify O–H and N–H protons.Open →
- Combining elemental analysis, mass spectrometry, IR and NMRRecall questions on what each technique contributes, why one alone is not enough, and how they are used together to separate possible isomers.Open →
- Molecular formula from the molecular ion, and fragmentation lossesRecall questions on scaling an empirical formula with the molecular ion peak, and on what losses of 15, 17, 29 and 45 mass units suggest.Open →
- What IR and NMR each contribute to a structureRecall questions on identifying functional groups from infrared absorptions and the fingerprint region, and on what chemical shift, integration and splitting each add.Open →
- Infrared absorption, global warming and breathalysersRecall questions on how covalent bonds absorb infrared radiation, greenhouse gases and the evidence linking carbon dioxide to global warming, and infrared monitoring of exhaust gases and breathalysers.Open →
- A systematic approach and the degree of unsaturationRecall questions on the order in which the techniques are applied, calculating the degree of unsaturation, and why a carbon-13 spectrum may show fewer peaks than carbons.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What does a singlet in proton NMR indicate about adjacent protons?
Key term
What compound is used as the reference standard for chemical shift measurements in NMR spectroscopy?
Key term
Why are deuterated solvents such as CDCl₃ used when running NMR spectra?
Key term
How can O–H and N–H protons be identified using D₂O in proton NMR?
Numbers
What two pieces of information does mass spectrometry give, which technique turns an empirical formula into a molecular formula, and how are isomers with the same molecular formula told apart?
Numbers
After dividing percentage compositions by relative atomic masses, what comes next, what does mass spectrometry provide, and how is the molecular ion mass then used?
Numbers
How does infrared spectroscopy distinguish carboxylic acids and alcohols from aldehydes, ketones and esters, what does the number of ¹H NMR peaks show, and what do proton chemical shifts indicate?
Key term
What do carbon-13 chemical shifts indicate, which technique identifies functional groups in a systematic structure elucidation, and what is the final step?
Key term
What is the n+1 rule, and what do a singlet and a doublet say about neighbouring hydrogens?
Key term
What does a quartet in a ¹H NMR spectrum tell you about neighbouring hydrogens?
Process
How does an infrared breathalyser measure the ethanol in a driver's breath?
Process
Which two gases from car exhausts can be monitored using infrared spectroscopy?
Process
Which bonds in carbon dioxide, water vapour and methane absorb infrared radiation in the atmosphere?
Key term
What does observing fewer ¹³C NMR peaks than carbon atoms indicate about the molecule?
Numbers
Define degree of unsaturation (index of hydrogen deficiency).
Process
What does 'proton decoupled' mean in the context of carbon-13 NMR spectra?
Process
How do propan-1-ol and propan-2-ol differ in ¹³C NMR?
Process
When determining molecular formula from empirical formula, what must first be calculated?
Take Spectroscopy further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Chemical shift vs Integration trace
Chemical shift: resonance position measured relative to a reference signal. Integration trace: relative area showing the proton ratio in different environments.
Carbon-13 NMR vs Proton NMR
Carbon-13 NMR: spectroscopy showing distinct carbon environments. Proton NMR: spectroscopy showing hydrogen environments, ratios and splitting.
Molecular ion peak vs Fragment ion peak
Molecular ion peak: signal corresponding to the intact ionised molecule. Fragment ion peak: signal corresponding to a charged piece formed after bond breaking.
Questions from this topic
Each one with the model answer underneath.
- 1
In carbon-13 NMR spectroscopy, what does the number of peaks in a spectrum indicate?
Model answer
The number of different carbon environments in the molecule.
- 2
Why do equivalent carbon atoms produce only a single peak in carbon-13 NMR?
Model answer
Because they are in identical chemical environments and therefore resonate at the same frequency.
- 3
What information do chemical shift values provide in carbon-13 NMR?
Model answer
They indicate the type of carbon environment present in the molecule.
- 4
What does 'proton decoupled' mean in the context of carbon-13 NMR spectra?
Model answer
Each carbon environment appears as a single peak rather than being split by coupling to attached protons.
- 5
How can carbon-13 NMR data be used to deduce molecular structures?
Model answer
By combining the number of carbon environments with their chemical shift values to identify the types and arrangements of carbon atoms present.
- 6
In proton NMR spectroscopy, what does the number of peaks indicate?
Model answer
The number of different proton environments in the molecule.
What is inside Levo
Six ways to work the same material.
Spectroscopy revision questions
- What does Spectroscopy cover in OCR A-Level Chemistry?
- 8 subtopics: carbon-13 and proton nmr: peaks, chemical shift and integration, spin-spin splitting and predicting a spectrum, tms, deuterated solvents and the d₂o shake, combining elemental analysis, mass spectrometry, ir and nmr, molecular formula from the molecular ion, and fragmentation losses, what ir and nmr each contribute to a structure, infrared absorption, global warming and breathalysers and a systematic approach and the degree of unsaturation. Each one has its own page with questions and model answers.
- How is Spectroscopy organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Spectroscopy, 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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