Numbers
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
Mathematical Skills in Chemistry
- 9 subtopics
- 23 things to know
- Components 01, 02 and 03
What Mathematical Skills in Chemistry covers
The mathematical requirements, assessed across all three components: units and standard form, handling data and significant figures, rearranging and substituting into the standard equations, reading graphs and spectra, and the geometry of molecules.
Where it is assessed
Components 01, 02 and 03
Storyline content, drawn on by all three written papers.
Check the OCR specification ↗The 9 subtopics
Each one has its own page.
- Units, standard form and the mole in calculationsRecall questions on converting volumes and pressures, deducing the units of Kc and of a rate constant, standard form, and mole calculations.Open →
- Yield, atom economy and logarithmic quantitiesRecall questions on percentage yield and atom economy, why a yield cannot exceed 100%, and converting between pH, [H⁺], Ka and pKa.Open →
- Significant figures, means and handling dataRecall questions on counting significant figures, taking the mean of concordant titres, and quoting a result to the precision the data allow.Open →
- Symbols, and rearranging the standard equationsRecall questions on what the equilibrium, proportionality and approximation symbols mean, and rearranging n = cV, pV = nRT and q = mcΔT.Open →
- Substituting into rearranged equationsRecall questions on working numbers through a rearranged equation for enthalpy, gas volume, Kc, rate and pH.Open →
- Reading spectra and kinetics graphsRecall questions on the axes of a mass spectrum and an infrared spectrum, the integration trace, and reading order from a kinetics graph.Open →
- Gradients, calibration lines and the Arrhenius plotRecall questions on choosing scales, lines of best fit and tangents, calibration lines, and what the gradient and intercept of an Arrhenius plot give.Open →
- Shapes and bond angles from electron pair repulsionRecall questions on the shapes and bond angles of the common molecules and ions, and why lone pairs close the angle.Open →
- Chiral centres, E/Z isomerism and optical activityRecall questions on identifying a chiral centre, the condition for E/Z isomerism, how optical isomers differ, and why a racemic mixture does not rotate light.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What amount is 3.01 × 10²² atoms, what is the percentage yield when 3.30 g is obtained from a 4.40 g theoretical yield, and why can a percentage yield never exceed 100%?
Numbers
Why does an addition reaction have 100% atom economy, how does Kc change when an exothermic reaction is heated, and what is the estimated mass of 0.49 mol of calcium carbonate (Mᵣ 100)?
Numbers
A solution has pH 3.40. What is [H⁺]?
Numbers
Why can a 0.10 mol dm⁻³ solution of a weak acid not have a pH of 1.0?
Numbers
How many significant figures are in 0.00340 and in 250.0, and what is the mean of three concordant titres?
Evaluation
A solid is weighed by difference on a balance whose readings are uncertain by ±0.005 g. What is the uncertainty in the mass transferred?
Key term
Why must the isotopic abundances used in such a calculation add up to 100%?
Numbers
How are n = cV, pV = nRT and q = mcΔT rearranged to make concentration, temperature and temperature change the subject?
Numbers
Rearrange pH = −log[H⁺] to make [H⁺] the subject.
Numbers
What is the pH of a solution in which [H⁺] = 5.0 × 10⁻⁴ mol dm⁻³?
Numbers
Methanoic acid has Kₐ = 1.6 × 10⁻⁴ mol dm⁻³. What is its pKₐ?
Numbers
What are the axes of a mass spectrum and of an infrared spectrum, and what does a strong absorption near 1700 cm⁻¹ suggest?
Numbers
Where are time and the volume of gas evolved plotted, what do the gradient and intercept of an Arrhenius plot give, and what is Eₐ for a gradient of −7.20 × 10³ K?
Numbers
The same plot has an intercept of ln A = 30.0. What is A for this first-order reaction?
Numbers
A gas is evolved at a constant rate and 60.0 cm³ is collected in 40 s. What is the rate of gas production?
Key term
Place lone pair–lone pair, lone pair–bonding pair and bonding pair–bonding pair repulsions in order of decreasing strength.
Key term
What is the shape of a six-coordinate aqua complex of a transition metal, and what are the bond angles?
Key term
Give the bond angle around each carbon atom in diamond and in a layer of graphite.
Key term
What is the bond angle within a benzene ring, and what shape is the molecule?
Process
In a three-dimensional structural representation, what do a solid wedge and a dashed line indicate?
Process
What structural feature is required for a molecule to show E/Z isomerism?
Process
Which of but-1-ene and but-2-ene shows E/Z isomerism, and why?
Take Mathematical Skills in Chemistry further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Mean vs Median
Mean: the sum of the values divided by how many there are. Median: the middle value once the results are placed in order.
Significant figures vs Decimal places
Significant figures: the digits in a value that carry real information about its precision. Decimal places: the count of digits written after the decimal point.
Percentage uncertainty vs Percentage error
Percentage uncertainty: the uncertainty in a measurement expressed as a proportion of that measurement. Percentage error: the difference from the accepted value expressed as a proportion of it.
Questions from this topic
Each one with the model answer underneath.
- 1
Convert 750 cm³ to dm³.
Model answer
750 cm³ is 0.750 dm³.
- 2
Give the units of Kc for the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g).
Model answer
Kc = [NH₃]²/([N₂][H₂]³), so the units are (mol dm⁻³)² ÷ (mol dm⁻³)⁴, which simplifies to mol⁻² dm⁶.
- 3
Give the units of Kc for H₂(g) + I₂(g) ⇌ 2HI(g).
Model answer
There are two moles of gas on each side, so the concentration units cancel and Kc has no units.
- 4
State the units of the rate constant for a first-order, a second-order and a zero-order reaction.
Model answer
They are s⁻¹ for first order, dm³ mol⁻¹ s⁻¹ for second order and mol dm⁻³ s⁻¹ for zero order.
- 5
Express the gas constant 8.314 J mol⁻¹ K⁻¹ in kJ mol⁻¹ K⁻¹.
Model answer
It is 8.314 × 10⁻³ kJ mol⁻¹ K⁻¹.
- 6
Write 0.0050 mol dm⁻³ in standard form.
Model answer
It is 5.0 × 10⁻³ mol dm⁻³, retaining the two significant figures.
What is inside Levo
Six ways to work the same material.
Mathematical Skills in Chemistry revision questions
- What does Mathematical Skills in Chemistry cover in OCR A-Level Chemistry B?
- 9 subtopics: units, standard form and the mole in calculations, yield, atom economy and logarithmic quantities, significant figures, means and handling data, symbols, and rearranging the standard equations, substituting into rearranged equations, reading spectra and kinetics graphs, gradients, calibration lines and the arrhenius plot, shapes and bond angles from electron pair repulsion and chiral centres, e/z isomerism and optical activity. Each one has its own page with questions and model answers.
- How is Mathematical Skills in Chemistry organised?
- By the OCR H433 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Mathematical Skills in Chemistry, on a schedule.
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