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
Alkenes
- 6 subtopics
- 13 things to know
- Components 02 and 03
What Alkenes covers
The double bond and what it does: sigma and pi bonding, E/Z isomerism, the addition reactions and their electrophilic mechanism with Markownikoff's rule, and addition polymers and their disposal.
Where it is assessed
Components 02 and 03
Synthesis and Analytical Techniques, then the unified paper.
Check the OCR specification ↗The 6 subtopics
Each one has its own page.
- Alkenes: the double bond, sigma and pi bonding, and shapeRecall questions on unsaturation, how the sigma and pi bonds form, why there is no free rotation, and the trigonal planar shape and its angle.Open →
- E/Z and cis-trans isomerism in alkenesRecall questions on what causes E/Z isomerism, the structural requirement at each carbon, the Cahn-Ingold-Prelog priority rules, and when cis and trans may be used instead.Open →
- Hydrogenation, halogenation and hydration of alkenesRecall questions on the reagents and catalysts for each addition, the bromine water test and what a positive result shows, and the products formed.Open →
- Electrophilic addition, carbocation stability and Markownikoff's ruleRecall questions on why an electrophile is attracted to the double bond, the intermediate formed, the order of carbocation stability, and predicting the major product.Open →
- Addition polymerisation and repeat unitsRecall questions on what happens to the double bond, deducing a repeat unit from a monomer and a monomer from a polymer, and naming the common addition polymers.Open →
- Waste polymers, and biodegradable and photodegradable alternativesRecall questions on combustion and feedstock recycling, why burning PVC gives hydrogen chloride, and what biodegradable and photodegradable polymers achieve.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What are stereoisomers, what must each carbon of the double bond carry, and which rules assign E and Z?
Numbers
When may E and Z be treated as trans and cis, what does 'cis' indicate, and what must you check on each carbon of the double bond?
Numbers
If both carbons of a C=C bond each have two different substituents attached, what can you conclude about stereoisomerism?
Key term
Where do the two halogen atoms end up when a halogen adds to an alkene, what type of compound forms, and what colour is bromine water before it reacts?
Numbers
What reagent and catalyst are used in the industrial hydration of alkenes, and what is formed?
Numbers
What is an electrophile, why is it attracted to the C=C bond, and what intermediate forms?
Key term
According to Markownikoff's rule, to which carbon does the hydrogen atom of a hydrogen halide add?
Process
How does the stability of a secondary carbocation compare to primary and tertiary carbocations?
Process
After the double bond opens in addition polymerisation, how does each carbon atom become bonded to the growing chain?
Key term
What polymer is formed when propene undergoes addition polymerisation?
Key term
What toxic gas comes from burning PVC and why, and what is a biodegradable polymer?
Key term
Define the term photodegradable polymer.
Take Alkenes further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
E isomer vs Z isomer
E isomer: higher-priority groups positioned on opposite sides of a double bond. Z isomer: higher-priority groups positioned on the same side of a double bond.
Addition reaction vs Substitution reaction
Addition reaction: two reactants combining to form one product. Substitution reaction: one atom or group replacing another.
Addition polymer vs Condensation polymer
Addition polymer: a macromolecule formed without loss of a small molecule. Condensation polymer: a macromolecule formed with elimination of a small molecule.
Questions from this topic
Each one with the model answer underneath.
- 1
What does it mean for alkenes to be described as unsaturated hydrocarbons?
Model answer
They contain fewer than the maximum number of hydrogen atoms per carbon atom due to the presence of a carbon-carbon double bond.
- 2
What two types of bond make up the carbon-carbon double bond in an alkene?
Model answer
One sigma (σ) bond and one pi (π) bond.
- 3
How is a sigma bond formed between two carbon atoms?
Model answer
By the direct (head-on) overlap of orbitals along the axis between the two bonding carbon atoms.
- 4
Describe how a pi bond is formed in an alkene.
Model answer
By the sideways overlap of adjacent p-orbitals, creating regions of electron density above and below the plane of the bonding carbon atoms.
- 5
Why is there no free rotation about the carbon-carbon double bond in alkenes?
Model answer
Rotation would break the sideways overlap of the p-orbitals that form the pi bond.
- 6
What is the shape around each carbon atom involved in the C=C double bond of an alkene?
Model answer
Trigonal planar.
What is inside Levo
Six ways to work the same material.
Alkenes revision questions
- What does Alkenes cover in OCR A-Level Chemistry?
- 6 subtopics: alkenes: the double bond, sigma and pi bonding, and shape, e/z and cis-trans isomerism in alkenes, hydrogenation, halogenation and hydration of alkenes, electrophilic addition, carbocation stability and markownikoff's rule, addition polymerisation and repeat units and waste polymers, and biodegradable and photodegradable alternatives. Each one has its own page with questions and model answers.
- How is Alkenes organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Alkenes, 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.
Or £46 a year, about £3.83 a month. Cancel anytime.