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
Polymers and Life
- 21 subtopics
- 59 things to know
- Components 01, 02 and 03
What Polymers and Life covers
The storyline that carries the nitrogen-containing groups and the biological polymers: amino acids and proteins, DNA and RNA, enzymes as catalysts, acids, amines and amides, condensation polymerisation, optical isomerism, and NMR.
Where it is assessed
Components 01, 02 and 03
Storyline content, drawn on by all three written papers.
Check the OCR specification ↗The 21 subtopics
Each one has its own page.
- Amino acids, the peptide link and hydrolysing a proteinRecall questions on the general formula of an amino acid, which groups form the peptide link and what is lost, and the products of acid and alkaline hydrolysis.Open →
- Chromatography of amino acids and Rf valuesRecall questions on the baseline and solvent front, why a locating agent is needed, ninhydrin, and calculating and using an Rf value.Open →
- Protein structureRecall questions on primary, secondary and tertiary structure, the interactions between side chains, disulfide bridges, and fibrous against globular proteins.Open →
- DNA and RNA structureRecall questions on the sugars, the nucleotide monomer, the phosphate backbone, and how RNA differs from DNA in structure and stability.Open →
- Base pairing and the genetic codeRecall questions on which bases pair and by how many hydrogen bonds, why replication is semi-conservative, and reading an amino acid sequence from codons.Open →
- Molecular recognitionRecall questions on why shape and functional groups decide activity, why drug-receptor bonds must be weak, and why only some related compounds work.Open →
- Enzyme kineticsRecall questions on the shape of the rate-concentration curve, why it is first order then zero order, and why it levels off.Open →
- Characteristics of enzyme catalysisRecall questions on specificity, the effect of temperature and pH, the optimum, and why denaturation is not reversed on cooling.Open →
- Acidity of carboxylic acidsRecall questions on why a carboxylic acid is acidic, its reactions with metals, carbonates and alkalis, and why a phenol gives no effervescence.Open →
- Amino acids as zwitterionsRecall questions on why a zwitterion forms, the isoelectric point, and why amino acids melt high and dissolve well in water.Open →
- Basicity of aminesRecall questions on why the nitrogen lone pair makes an amine basic, the salt formed with an acid, and the smell and solubility of short-chain amines.Open →
- Naming acids, acyl chlorides, anhydrides, esters, aldehydes and ketonesRecall questions on the suffix for each series, writing a structural formula from a name, and naming a compound from its structure.Open →
- Diols, dicarboxylic acids, amines, amides and the nylonsRecall questions on naming diols and dicarboxylic acids, the primary and secondary amide groups, and the monomers behind nylon-6,6 and nylon-6.Open →
- Hydrolysis of esters and amidesRecall questions on acid and alkaline hydrolysis of an ester and an amide, why the alkaline route goes to completion, and recovering the free acid.Open →
- Reactions of acyl chloridesRecall questions on why an acyl chloride is so reactive, and its reactions with water, alcohols and amines and what is observed.Open →
- Condensation polymerisationRecall questions on what is eliminated, which monomer pairs give a polyester and which a polyamide, and deducing a repeat unit or the monomers.Open →
- Optical isomerismRecall questions on what a chiral centre is, identifying one in a structure, why the isomers are drawn in three dimensions, and racemic mixtures.Open →
- Further interpretation of mass spectraRecall questions on accurate mass and why it separates compounds of the same nominal mass, and identifying fragments lost from a molecular ion.Open →
- Chemical shift and equivalent protons in proton NMRRecall questions on the TMS reference, what chemical shift depends on, equivalent protons, and the shift ranges for the common environments.Open →
- The n + 1 rule, integration and carbon-13 NMRRecall questions on the splitting patterns and what they show, what the integration trace gives, and how a carbon-13 spectrum is read.Open →
- Combined spectroscopic structure determinationRecall questions on combining infrared, mass spectrometry and NMR, and on working a structure out from a set of spectra.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Which groups react to form a peptide link and what is eliminated, how many peptide links are in a polypeptide of eight amino acid residues, and what does alkaline hydrolysis of a peptide give?
Key term
Why is a chromatogram baseline drawn in pencil, why is a locating agent needed for amino acids, and which locating agent is used?
Key term
Why can an Rf value never be greater than 1?
Key term
Which part of a residue gives tertiary interactions, where do disulfide bridges form, and how do fibrous and globular proteins differ?
Process
Does denaturing a protein change its primary structure? Explain.
Process
Which sugar is in DNA and which in RNA, how do the two sugars differ, and how is a base attached to the backbone?
Key term
Which DNA base is replaced in RNA, which bases are purines, and which part of a nucleotide varies along a strand?
Process
Why is the outside of the double helix water soluble, how does the structure of RNA differ from DNA overall, and why is DNA more stable than RNA?
Evaluation
Why is it an advantage that the forces between the two strands are relatively weak?
Process
Why is a cytosine and guanine rich region harder to separate, what does complementary base pairing mean, and how does base pairing allow exact copying?
Process
Why does replication leave one old strand in each molecule, and what amino acid sequences come from codons GGU GCC CUG (glycine, alanine, leucine) and from coding DNA GAT CAA GTC (GAU aspartic acid, CAA glutamine, GUC valine)?
Process
Why does the primary structure alone determine a protein's function?
Key term
Why can a change of one base sometimes have no effect at all on the protein?
Numbers
Why can two different drugs share an effect, why must the bonds holding a drug to a receptor be weak, and why do only some of a series of related compounds show activity?
Key term
Why can one optical isomer of a drug be active while its mirror image is not?
Process
How does knowing the shape of a receptor site help in designing a medicine?
Numbers
How does the shape of the curve show first order at low substrate and zero order at high, and why?
Numbers
What is the unit of a first-order rate constant, what does doubling the enzyme do, and why does the curve level off?
Numbers
Why are initial rates measured, why is temperature control critical, and how is a coloured product followed?
Key term
Why is a very small amount of enzyme normally enough?
Numbers
Why does the rate rise towards the optimum temperature, fall steeply above it, and not recover on cooling?
Numbers
What would you observe about the maximum rate of a reaction in the presence of a competitive inhibitor?
Numbers
What is the equation for ethanoic acid with sodium carbonate, why is the carbonate reaction a useful test for a carboxylic acid, and why does a phenol give no effervescence?
Numbers
What are the products when a carboxylic acid reacts with an alkali and with a reactive metal, and what is the equation for propanoic acid with sodium hydroxide?
Numbers
Why does magnesium react less vigorously with ethanoic acid than with hydrochloric acid of the same concentration?
Key term
Why does an amino acid exist as a zwitterion, and why does that give high melting points and good water solubility?
Numbers
What are the equations for glycine with hydrochloric acid and with sodium hydroxide, and would an amino acid with a –COOH in its side chain have an isoelectric point above or below 7?
Numbers
What is the primary amine functional group, why is it basic, and what forms when it accepts a proton?
Key term
What is seen when a volatile amine meets hydrogen chloride fumes, why do short-chain amines dissolve well in water, and why is the amino group of an amino acid protonated at low pH?
Key term
Why is an amide much less basic than an amine?
Key term
Which suffixes identify a carboxylic acid and an acyl chloride, and how is an ester named?
Key term
What suffix is used for an aldehyde, and where must its functional group lie?
Key term
Why does hexanedioic acid keep the number six in its name even though only four CH₂ groups appear?
Numbers
What is the equation for the acid hydrolysis of ethyl ethanoate, why is it an equilibrium, and what is the equation for methyl propanoate with sodium hydroxide?
Numbers
Why does alkaline hydrolysis of an ester go to completion, how is the free carboxylic acid recovered, and what is the equation for ethanamide with hydrochloric acid?
Numbers
What are the products when ethanamide is hydrolysed by sodium hydroxide, when a secondary amide is hydrolysed by aqueous alkali, and when nylon-6,6 is hydrolysed by hot concentrated acid?
Numbers
Why is an acyl chloride more reactive than the carboxylic acid, and what is the equation for, and what is seen when, ethanoyl chloride meets ethanol?
Numbers
What is the equation for ethanoyl chloride with methylamine, why is excess amine used, and which part attacks?
Key term
Name the ester and the other product formed when propanoyl chloride reacts with methanol.
Key term
How can you tell from the repeat unit that a polymer is a polyamide rather than a polyester?
Key term
Why do many condensation polymers slowly weaken in a damp environment?
Process
How do you decide whether a carbon is a chiral centre, why must enantiomers be drawn three-dimensionally, and why does a laboratory synthesis give a racemic mixture?
Key term
Why does a reaction catalysed by an enzyme usually give only one enantiomer?
Key term
Why is optical isomerism a form of stereoisomerism rather than structural isomerism?
Numbers
Why do compounds of the same nominal mass differ in accurate mass, which atom is the standard, and how does an M⁺ at m/z 180.0420 fit C₉H₈O₄?
Numbers
Why must an accurate mass be quoted to four decimal places, and what is lost to give peaks at 138 and 120 from 180?
Key term
Why can a mass difference alone sometimes not identify the group lost with certainty?
Key term
How can a series of mass differences help build up a structure?
Numbers
Which compound is the NMR reference, how many peaks does ethanol give, and what does a triplet indicate?
Key term
Predict the splitting patterns of the two proton signals of bromoethane, CH₃CH₂Br.
Key term
Why does the CH₃ signal of propanone appear as a single peak?
Numbers
Why is it worth starting from the high-resolution molecular ion rather than the infrared spectrum?
Numbers
Why can mass spectrometry not usually decide between two isomers on its own?
Key term
Between which residues do disulfide bridges form?
Key term
Which two functional groups give an amino acid its acid–base behaviour?
Key term
What suffix identifies an acyl chloride?
Key term
Compare the mass of the repeat unit with the mass of the monomers in each type of polymerisation.
Key term
Which compound is used as the reference standard in NMR, and what shift is it given?
Take Polymers and Life further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Addition polymerisation vs Condensation polymerisation
Addition polymerisation: monomers joining across a double bond with no other product formed. Condensation polymerisation: monomers joining with a small molecule such as water eliminated each time.
Peptide link vs Ester link
Peptide link: the amide linkage joining two amino acid residues. Ester link: the linkage formed between a carboxylic acid group and an alcohol group.
Zwitterion vs Isoelectric point
Zwitterion: a species carrying both a positive and a negative charge but neutral overall. Isoelectric point: the pH at which an amino acid carries no overall charge.
Questions from this topic
Each one with the model answer underneath.
- 1
Which four groups are bonded to the central carbon atom of an amino acid?
Model answer
An amino group NH₂, a carboxyl group COOH, a hydrogen atom and a side chain R.
- 2
Give the general formula of an amino acid.
Model answer
The general formula is RCH(NH₂)COOH, where R is the side chain that differs from one amino acid to the next.
- 3
Which carbon atom in an amino acid carries the amino group?
Model answer
The carbon atom immediately next to the carboxyl group, so the amino group is always on carbon 2.
- 4
Name the link that joins two amino acids together.
Model answer
The peptide link, –CO–NH–, which is an amide link.
- 5
Which two functional groups react when a peptide link forms, and what is eliminated?
Model answer
The COOH of one amino acid reacts with the NH₂ of another, and a molecule of water is eliminated.
- 6
Why are proteins classified as condensation polymers rather than addition polymers?
Model answer
Their monomers join with the loss of a small molecule, water, at every link, so the repeat unit is lighter than the monomer it came from.
What is inside Levo
Six ways to work the same material.
Polymers and Life revision questions
- What does Polymers and Life cover in OCR A-Level Chemistry B?
- 21 subtopics: amino acids, the peptide link and hydrolysing a protein, chromatography of amino acids and rf values, protein structure, dna and rna structure, base pairing and the genetic code, molecular recognition, enzyme kinetics, characteristics of enzyme catalysis, acidity of carboxylic acids, amino acids as zwitterions, basicity of amines, naming acids, acyl chlorides, anhydrides, esters, aldehydes and ketones, diols, dicarboxylic acids, amines, amides and the nylons, hydrolysis of esters and amides, reactions of acyl chlorides, condensation polymerisation, optical isomerism, further interpretation of mass spectra, chemical shift and equivalent protons in proton nmr, the n + 1 rule, integration and carbon-13 nmr and combined spectroscopic structure determination. Each one has its own page with questions and model answers.
- How is Polymers and Life organised?
- By the OCR H433 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Polymers and Life, 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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