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
Transition Elements
- 10 subtopics
- 24 things to know
- Components 01 and 03
What Transition Elements covers
Ligands and complex ions, their shapes and stereoisomerism including cisplatin, ligand substitution and haemoglobin, and the coloured precipitates and redox interconversions that identify the transition metal ions.
Where it is assessed
Components 01 and 03
Periodic Table, Elements and Physical Chemistry, then the unified paper.
Check the OCR specification ↗The 10 subtopics
Each one has its own page.
- Ligands, complex ions and coordination numberRecall questions on monodentate and bidentate ligands, what a complex ion is, and what coordination number means.Open →
- Electron configurations from Sc to Zn, and which are transition elementsRecall questions on the electron configurations of scandium to zinc and their ions, the chromium and copper exceptions, the definition of a transition element, and why scandium and zinc are excluded.Open →
- Variable oxidation states, coloured ions and catalysisRecall questions on the variable oxidation states and coloured ions of transition elements, colourless Sc³⁺ and Zn²⁺, and catalysis by transition metals and their compounds, from manganese(IV) oxide to industrial processes.Open →
- The shapes of complexes, stereoisomerism and cisplatinRecall questions on six-fold and four-fold coordination geometries, cis-trans and optical isomerism in complexes, and how cisplatin works and its risks.Open →
- Ligand substitution, haemoglobin and the copper complexesRecall questions on what ligand substitution is, oxygen and carbon monoxide at the iron centre of haemoglobin, and the copper complexes formed with ammonia and chloride.Open →
- Hydroxide precipitates of iron, manganese and chromiumRecall questions on the colour and identity of each precipitate with sodium hydroxide, and which dissolve in excess alkali or excess ammonia.Open →
- Redox interconversions of iron, chromium and copperRecall questions on the reagents that interconvert iron(II) and iron(III) and chromium(III) and dichromate(VI), the colour changes, and the disproportionation of copper(I).Open →
- Why ligand substitution happens and the changes it causesRecall questions on bond strength and stability as the drivers, and on when substitution changes the coordination number and geometry and when it does not.Open →
- Precipitation reactions written as aqua complexesRecall questions on why these reactions can be written with aqua complexes, and on the two ways of writing the copper(II) ion and its hydroxide.Open →
- Dissolving hydroxides in excess ammonia and distinguishing the ionsRecall questions on which hydroxides dissolve in excess ammonia and which do not, the complexes formed, and using the tests to tell the ions apart.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is the electron configuration of an iron atom (atomic number 26)?
Key term
What is the electron configuration of a scandium atom (atomic number 21)?
Process
Which elements in Period 4 are transition elements?
Key term
What is observed when manganese(IV) oxide is added to hydrogen peroxide solution?
Process
Why are aqueous solutions of Sc³⁺ and Zn²⁺ ions colourless?
Evaluation
Evaluate the use of transition metal catalysts in the chemical industry.
Key term
What shape goes with six-fold coordination, and what are the geometries of the hexaaquacopper(II) ion and the tetrachlorocuprate(II) ion?
Key term
What is the geometry of cisplatin, what type of stereoisomerism can complexes show, and how are the ligands arranged in cisplatin?
Process
What is seen when sodium hydroxide is added to aqueous copper(II) ions, what happens with ammonia initially and in excess, and what complex forms?
Process
What is ligand substitution, what happens with excess ammonia and chromium(III), and how does oxygen bind in haemoglobin?
Key term
Which reagent and conditions oxidise chromium(III) to chromate(VI), which reagent reduces dichromate(VI) back to chromium(III), and what is disproportionation?
Key term
What is the identity of the precipitate formed when Fe²⁺(aq) reacts with OH⁻(aq)?
Key term
What colour precipitate forms when aqueous manganese(II) ions react with sodium hydroxide?
Key term
What compound is formed as a precipitate when Cr³⁺(aq) reacts with OH⁻(aq)?
Key term
What is observed when aqueous iron(III) ions react with sodium hydroxide?
Numbers
Why does ligand substitution occur, and how many water ligands does excess ammonia replace in the hexaaquacopper(II) ion?
Process
How many water ligands do excess chloride ions replace in the hexaaquacopper(II) ion, how does the geometry change, and what happens to aqueous cobalt(II) in excess ammonia?
Key term
Under what condition does ligand substitution result in a change in coordination number?
Numbers
Why can precipitation reactions be written with aqua ion formulae, why can hydroxide precipitates be written as aqua complexes, and what happens when excess sodium hydroxide is added to Cr(OH)₃?
Numbers
What precipitate forms when Cr³⁺(aq) meets hydroxide ions, why does it dissolve in excess sodium hydroxide, and what complex ion forms?
Key term
What complex forms when chromium(III) hydroxide dissolves in excess ammonia, what is the formula of the copper–ammonia complex, and why does the copper solution turn deep blue?
Key term
How could you distinguish between Fe²⁺ and Fe³⁺ ions using aqueous sodium hydroxide?
Key term
What colour precipitate forms when aqueous sodium hydroxide is added to a solution containing Cu²⁺ ions?
Take Transition Elements further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Ligand vs Complex ion
Ligand: an electron-pair donor forming a coordinate bond to a metal ion. Complex ion: a charged metal centre surrounded by coordinate-bonded species.
Monodentate ligand vs Bidentate ligand
Monodentate ligand: an electron-pair donor forming one coordinate bond. Bidentate ligand: an electron-pair donor forming two coordinate bonds.
Ligand substitution vs Precipitation
Ligand substitution: replacement of one electron-pair donor around a metal centre. Precipitation: formation of an insoluble solid from aqueous ions.
Questions from this topic
Each one with the model answer underneath.
- 1
What is a ligand?
Model answer
A species that donates a lone pair of electrons to a metal ion or metal atom to form a coordinate (dative covalent) bond.
- 2
What defines a monodentate ligand?
Model answer
A ligand that donates one lone pair of electrons to form one coordinate bond with the central metal ion.
- 3
What defines a bidentate ligand?
Model answer
A ligand that donates two lone pairs of electrons to form two coordinate bonds with the central metal ion.
- 4
Is water a monodentate or bidentate ligand?
Model answer
Monodentate.
- 5
Classify the chloride ion as a ligand type.
Model answer
Monodentate ligand.
- 6
Is ammonia a monodentate or bidentate ligand?
Model answer
Monodentate.
What is inside Levo
Six ways to work the same material.
Transition Elements revision questions
- What does Transition Elements cover in OCR A-Level Chemistry?
- 10 subtopics: ligands, complex ions and coordination number, electron configurations from sc to zn, and which are transition elements, variable oxidation states, coloured ions and catalysis, the shapes of complexes, stereoisomerism and cisplatin, ligand substitution, haemoglobin and the copper complexes, hydroxide precipitates of iron, manganese and chromium, redox interconversions of iron, chromium and copper, why ligand substitution happens and the changes it causes, precipitation reactions written as aqua complexes and dissolving hydroxides in excess ammonia and distinguishing the ions. Each one has its own page with questions and model answers.
- How is Transition Elements organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Transition Elements, 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.