Key term
OCR A-Level Chemistry B H433
Development of Practical Skills in Chemistry
Topic overviewPlanning experimentsImplementing: apparatus, units and recording dataSignificant figures and titration calculationsGraphs, gradients and drawing a conclusionAnomalous results, precision, accuracy and types of errorCalculating uncertainties and improving a methodHazards, risk and control measuresRecording, processing and judging dataMeasuring pH, mass and volume, and choosing an indicatorReflux, distillation, purification and the standard testsPAG1 to PAG6: moles, enthalpy, qualitative analysis and organic synthesisPAG7 to PAG12: electrochemistry, rates and pH
Elements of Life
Topic overviewThe mole, relative masses and empirical formulaeConcentration, titration and writing balanced equationsOrbitals, sub-shells and electron configurationsSub-atomic particles and the evidence for the model of the atomFusion reactions and the origin of the elementsIonic, covalent, dative and metallic bonding and the four structuresMelting point, conductivity and solubility of each structureShapes of molecules and ionsThe periodic table, the blocks and trends in melting pointIon charges, the common polyatomic ions and writing formulaeGroup 2 chemistry and charge densityIonisation enthalpy and trends in reactivitySolubility rules and the tests for the common anionsHydroxide precipitates, ionic equations and identifying an unknown saltAcids, bases and preparing saltsThe electromagnetic spectrum and photon energy calculationsEmission and absorption spectra, and flame testsMass spectrometry and relative atomic mass
Developing Fuels
Topic overviewMolar gas volume and the ideal gas equationGas volume calculations and measuring a gas in the laboratoryBonding and shape in organic moleculesEnthalpy changes: definitions and standard conditionsBond enthalpiesq = mcΔT and measuring an enthalpy change in solutionBurning a fuel, correcting for heat loss, and the assumptions madeHess' law and enthalpy cyclesCatalysts, heterogeneous catalysis and catalyst poisonsCracking and how it is carried outThe pollutants from burning fuels and their effectsCatalytic converters and cutting emissionsAliphatic and aromatic compounds, functional groups and general formulaeDeducing formulae and naming a branched compoundCombustion of organic compoundsAddition of bromine and hydrogen halides, and the test for unsaturationHydrogenation and hydration of alkenesAddition polymerisationElectrophilic addition mechanismDisplayed, shortened and skeletal formulaeChain, position and functional group isomerismWhy alkenes show stereoisomerism, and the E/Z and cis/trans rulesNaming and comparing the stereoisomersSustainable fuels: benefits and risks
Elements From the Sea
Topic overviewAtom economyExtraction of the halogens from sea mineralsElectrolysis of molten salts and writing electrode half-equationsElectrolysis of aqueous solutions and the electrolysis of brineRedox as electron transferThe rules for assigning oxidation statesOxidation state calculations, and defining oxidation and reductionBalancing a redox equation with oxidation statesThe iodine-thiosulfate titration and its calculationsSystematic nomenclature of inorganic compoundsPhysical properties of the halogensHalogen reactivity and the displacement equationsObserving a displacement, and using an organic solvent or starchSilver halide precipitation and testsPreparation of the hydrogen halidesProperties of the hydrogen halidesChlorine: risks, benefits and usesDynamic equilibriumWriting a Kc expression and calculating KcWhat the magnitude of Kc tells you, and what changes itUsing the Kc expression to explain a shift in positionTemperature, pressure and catalysts on an equilibrium
The Ozone Story
Topic overviewElectronegativity and bond polarityIntermolecular bondsBoiling points and intermolecular bondsActivation enthalpy and enthalpy profilesCollision theory and the Boltzmann distributionFollowing a reaction and finding the rate from a graphCatalysts and alternative reaction routesHomogeneous catalysis and intermediatesComposition of gas mixtures by volumeRecognising and naming haloalkanesPrimary, secondary and tertiary haloalkanes, and the aminesProperties and nucleophilic substitution of haloalkanesSubstitution, nucleophiles and the SN2 mechanismRelative reactivity of the haloalkanesHomolytic and heterolytic fission, radicals and half curly arrowsInitiation, propagation and termination in a radical chain reactionOzone depletion by haloalkanesOzone in the stratosphere and troposphereRadiation of the Earth and the SunEffects of UV and visible radiation on moleculesCalculations with frequency, wavelength and energy
What's in a Medicine?
Topic overviewFormulae of oxygen-containing homologous seriesPrimary, secondary and tertiary alcoholsThe acidity of phenol compared with alcohols and carboxylic acidsThe iron(III) chloride test and esterifying a phenolEsterification and oxidising primary, secondary and tertiary alcoholsDehydration, halogenation and planning a two-step synthesisPreparing aspirin, filtering under reduced pressure and recrystallisationThin layer chromatography, Rf values and percentage yieldReflux and distillation in an organic preparationWashing, drying and redistilling a liquid productThe aims of green chemistry and atom economyCatalysts, renewable feedstocks and measuring greennessElimination reactionsThe molecular ion and fragment ionsIdentifying a compound from its fragments and the M+1 peakHow infrared absorption works and the characteristic absorptionsReading a spectrum, the fingerprint region and combining techniques
The Chemical Industry
Topic overviewRate equations, order and the rate constantDeducing the units of k and rate calculationsHalf-livesContinuous monitoring, quenching and the initial rates methodReading order from concentration-time and rate-concentration graphsThe Arrhenius equation and what each symbol meansThe ln k against 1/T plot and finding the activation enthalpyRate-determining step and mechanismEffect of conditions on the magnitude of the equilibrium constantEconomic operating conditions for an industrial processWriting a Kc expression and deducing its unitsICE-table calculations and measuring Kc experimentallyChemical reactions in industrial processesNitrogen, ammonia and the ammonium ionOxidation states of nitrogen and the tests for nitrate and ammoniumCosts, benefits and risks of industrial processes
Polymers and Life
Topic overviewAmino acids, the peptide link and hydrolysing a proteinChromatography of amino acids and Rf valuesProtein structureDNA and RNA structureBase pairing and the genetic codeMolecular recognitionEnzyme kineticsCharacteristics of enzyme catalysisAcidity of carboxylic acidsAmino acids as zwitterionsBasicity of aminesNaming acids, acyl chlorides, anhydrides, esters, aldehydes and ketonesDiols, dicarboxylic acids, amines, amides and the nylonsHydrolysis of esters and amidesReactions of acyl chloridesCondensation polymerisationOptical isomerismFurther interpretation of mass spectraChemical shift and equivalent protons in proton NMRThe n + 1 rule, integration and carbon-13 NMRCombined spectroscopic structure determination
Oceans
Topic overviewSolubility in aqueous and non-aqueous solventsLattice, hydration and solution enthalpies and how they relateMeasuring an enthalpy change of solutionCharge density and the size of enthalpy termsEntropy: qualitative treatmentTotal entropy change and the condition for feasibilityThe limiting temperature, and why a feasible reaction may not happenCalculating the entropy change of the systemThe solubility product expression, its units and calculationsPredicting precipitation and the common ion effectBronsted-Lowry theory of acids and basesStrong acids and strong basesWeak acids, Ka and pKapH of strong acids and strong basespH of weak acids, dilution and the limits of the approximationWhat a buffer is and how it resists a change in pHBuffer calculations, capacity and the natural buffersHow the greenhouse effect works and which gases cause itWhy a molecule absorbs, concentrations in ppm, and ocean chemistry
Developing Metals
Topic overviewManganate(VII) titrations and their calculationsThiosulfate titrations, recording results and good techniqueShapes of complexes and coordination numberBalancing redox equations involving acid-base reactionsSimple electrochemical cellsAction of an electrochemical cellStandard electrode potentials and calculating E°cellRusting and how it is preventedTransition metals: definition, oxidation states and coloursd-block electron configurations of the atoms and their ionsWhy transition metals show variable oxidation statesLigands and complex ionsCoordinate bonding and what makes a ligandBidentate and multidentate ligands, and finding a complex's formulaReactions of Fe2+, Fe3+ and Cu2+ with hydroxide and ammoniaCatalytic activity of transition metalsOrigin of colour in transition metal complexesColorimetry
Colour by Design
Topic overviewHow dyes attach to fibresStructure of a dye moleculeFats and oilsArenes and delocalisationRepresentations of benzene and enthalpy of hydrogenationTests for the common functional groupsIdentifying a polyfunctional molecule from a set of test resultsHalogenation and nitration of benzene and the electrophiles involvedThe nitration mechanism, sulfonation and the Friedel-Crafts reactionsDiazotisation and why it is done coldCoupling reactions, azo dyes and the route from benzeneOxidising an aldehyde and the three carbonyl testsCyanohydrin formation and its use in synthesisUsing the Data Sheet reactions to plan a routeChoosing between routes on yield and atom economyNucleophilic addition mechanismClassifying organic reactions and unfamiliar mechanismsOrigins of colour in organic moleculesHow gas-liquid chromatography separates a mixtureRetention time, peak area and the limits of the technique
Chemical Literacy
Mathematical Skills in Chemistry
Topic overviewUnits, standard form and the mole in calculationsYield, atom economy and logarithmic quantitiesSignificant figures, means and handling dataSymbols, and rearranging the standard equationsSubstituting into rearranged equationsReading spectra and kinetics graphsGradients, calibration lines and the Arrhenius plotShapes and bond angles from electron pair repulsionChiral centres, E/Z isomerism and optical activity
Development of Practical Skills in Chemistry
Reflux, distillation, purification and the standard tests
- 1 thing to know
- Components 01 and 03
Overview
Recall questions on reflux and distillation, separating and drying an organic layer, recrystallisation, melting point, Rf values and the standard test-tube tests.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Questions from this subtopic
Each one with the model answer underneath.
- 1
What does heating under reflux achieve, and why is the condenser vertical and open at the top?
Model answer
It allows a mixture to be boiled for a long period without loss of volatile material, because vapour condenses and runs back into the flask; the top is left open so pressure cannot build up, and anti-bumping granules are added so that boiling is smooth rather than violent.
- 2
In a simple distillation, where must the thermometer bulb be placed and why?
Model answer
The bulb sits level with the side arm leading to the condenser so that it measures the temperature of the vapour actually passing over.
- 3
How is a separating funnel used to purify an organic liquid, and what precaution must be taken?
Model answer
The mixture is shaken in the stoppered funnel, the layers allowed to settle, and the lower layer run off through the tap; the funnel must be inverted and the tap opened during shaking to release the pressure of any vapour or gas.
- 4
Which drying agent is added to a separated organic layer, and how do you know enough has been used?
Model answer
Anhydrous magnesium sulfate or sodium sulfate is added, and enough has been used when some of the solid remains as a free-running powder rather than clumping together.
- 5
How is a solid purified by recrystallisation, and why is the minimum volume of hot solvent used?
Model answer
The impure solid is dissolved in the minimum volume of hot solvent, filtered hot, then cooled so that crystals of the product form and are filtered off; using the minimum volume ensures the solution is saturated so that the maximum amount of product crystallises on cooling.
- 6
Why is a fluted filter paper used for hot filtration during recrystallisation?
Model answer
The folds increase the surface area available so the hot solution passes through quickly, before it can cool and deposit crystals in the funnel.
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