Key term
CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Topic overviewProtons, neutrons and electronsAtomic number, mass number and the composition of ionsIsotopes and relative isotopic massRelative atomic, molecular and formula massMass spectra and relative atomic mass calculationsMass spectra of diatomic elementsElectronic configuration and the building up principleOrbitals, electron spin and orbital shapesThe s-, p-, d- and f-blocks of the Periodic TableIonisation energies and their equationsTrends in ionisation energy as evidence for shells and subshells
Bonding
Topic overviewIonic bonding and electron transferDot and cross diagrams for ionic compoundsCovalent bonding and the shared pairLone pairs and co-ordinate bondingDot and cross diagrams for covalent molecules and ionsThe octet rule and its limitationsElectronegativity and bond polarityMetallic bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Topic overviewAlkanes as saturated hydrocarbonsBoiling points of alkanes and van der Waals' forcesBoiling points of branched isomersComplete and incomplete combustion of alkanesPollutants from alkane fuels and the atmosphereCatalytic convertersRadicals, homolytic fission and heterolytic fissionFree radical substitution of alkanes
Alkenes
Topic overviewUnsaturated hydrocarbons and the bromine water testSigma and pi bonds in the carbon–carbon double bondElectron density at C=C, reactivity and catalytic hydrogenationAddition of chlorine and bromine to alkenesAddition of hydrogen chloride and hydrogen bromideElectrophiles, heterolytic fission and the addition mechanismCarbocation stability and Markovnikov additionAddition polymerisation of alkenes
Halogenoalkanes
Topic overviewClassification and boiling points of halogenoalkanesLaboratory preparation of a halogenoalkane from an alcoholNucleophiles and hydrolysis with aqueous alkaliReactions with ammonia and with potassium cyanideRelative rates of hydrolysis and carbon–halogen bond enthalpyElimination using ethanolic potassium hydroxideCFCs and the ozone layer
Alcohols
Infrared Spectroscopy
Energetics
Topic overviewExothermic and endothermic changesStandard conditions and the standard enthalpy changeEnthalpy level diagramsStandard enthalpies of combustion and formationStandard enthalpy of neutralisationMeasuring enthalpy changes by experimentEnthalpy calculations using q = mcΔTHess's Law and enthalpy cyclesIndirect enthalpy calculations using Hess's LawAverage bond enthalpies and their limitations
Kinetics
Equilibrium
Group II Elements and Their Compounds
Topic overviews-block character and electronic configurationTrends in atomic radius and first ionisation energyReactions of the elements with oxygen, water and dilute acidsThe oxides and their reactions with water and dilute acidsThermal stability of the carbonates and hydroxidesUses of magnesium oxide, calcium carbonate and limeSolubility trends and solubility curves
Lattice Enthalpy, Entropy and Free Energy
Topic overviewLattice enthalpy and the factors that control itBorn–Haber cycles for Group I halidesBorn–Haber cycles for Group II halides and oxidesEnthalpy of hydration and enthalpy of solutionCalculations on dissolving ionic compoundsEntropy and the limits of enthalpy changeStandard entropy change calculationsFree energy and the temperature of feasibility
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Topic overviewEquilibrium concentrations from initial amountsKc expressions, values and unitsBrønsted–Lowry acids, bases and conjugate pairsKw, pH and the pH of strong acids and basesKa, pKa and the pH of weak acidsBuffer solutions and how they resist pH changeCalculating the pH of a buffer solutionTitration curves, indicators and the pH of salt solutions
Isomerism
Aldehydes and Ketones
Topic overviewStructure and naming of aldehydes and ketonesBoiling points and solubility of carbonyl compoundsPreparation from primary and secondary alcoholsReaction with hydrogen cyanide and the nucleophilic addition mechanismRacemic mixtures from nucleophilic addition2,4-dinitrophenylhydrazine and the identification of carbonylsDistinguishing aldehydes from ketones, and reduction with lithal
Carboxylic Acids
Derivatives of Carboxylic Acids
Topic overviewEsters and acyl chlorides: structure and namingBoiling points and solubility of monoestersMaking esters from alcohols with carboxylic acids or acyl chloridesThe laboratory preparation of a liquid esterFats and oils as esters of glycerolTransesterification, biodiesel and margarineReactions of acyl chlorides with water and alcohols
Aromatic Chemistry
Spectroscopy and Chromatography
Topic overviewThe mass spectrum: molecular ion and base peakFragmentation and the formulae of fragment ionsHigh resolution mass spectrometryNuclear magnetic resonance and the TMS standardChemically equivalent hydrogens and chemical shiftIntegration curvesSpin–spin splitting and the n+1 ruleDeducing a structure from an nmr spectrumPaper and thin-layer chromatographyGas–liquid chromatography
Volumetric Analysis
Transition Metals
Topic overviewThe characteristic properties of the transition metalsElectronic configurations of the metals and their ionsComplexes, ligands and coordination numberOxidation number, redox and disproportionationMonodentate, bidentate and polydentate ligandsLigand strength and the entropy of ligand replacementLigand replacement in copper(II) complexesThe colours of the aqueous transition metal ionsHydroxide precipitates with sodium hydroxidePrecipitates with aqueous ammonia and their dissolutionVanadium and the interconversion of its oxidation states
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Energetics
Indirect enthalpy calculations using Hess's Law
- 3 things to know
- Unit AS 2
Overview
Recall questions on using standard enthalpies of formation and of combustion in a Hess cycle, worked calculations on methane, calcium carbonate, ethene, the thermite reaction, iron ore and sulfur dioxide, working backwards to an unknown enthalpy of formation, and checking the sign of the answer.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe how standard enthalpies of combustion are used to find the enthalpy change of a reaction.
Numbers
Using ΔfHӨ values of −824 kJ mol⁻¹ for Fe₂O₃(s) and −1676 kJ mol⁻¹ for Al₂O₃(s), calculate ΔH for Fe₂O₃(s) + 2Al(s) → Al₂O₃(s) + 2Fe(s).
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe how standard enthalpies of formation are used to find the enthalpy change of a reaction.
Model answer
Each value is multiplied by the balancing number of that substance, the values for the reactants are added, the values for the products are added, and the reactant sum is subtracted from the product sum.
- 2
Describe how standard enthalpies of combustion are used to find the enthalpy change of a reaction.
Model answer
Each value is multiplied by the balancing number of that substance, and the sum for the products is subtracted from the sum for the reactants.
- 3
Using ΔfHӨ values of −75 kJ mol⁻¹ for CH₄(g), −394 kJ mol⁻¹ for CO₂(g) and −286 kJ mol⁻¹ for H₂O(l), calculate ΔH for CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).
Model answer
The products total −394 + 2 × −286, which is −966 kJ mol⁻¹, and the reactants total −75 kJ mol⁻¹, so ΔH is −966 minus −75, which is −891 kJ mol⁻¹.
- 4
Using ΔcHӨ values of −394 kJ mol⁻¹ for graphite, −286 kJ mol⁻¹ for hydrogen and −890 kJ mol⁻¹ for methane, calculate the standard enthalpy of formation of methane.
Model answer
The value is −394 + 2 × −286 − (−890), which is −394 − 572 + 890, giving −76 kJ mol⁻¹.
- 5
Using ΔfHӨ values of −1207 kJ mol⁻¹ for CaCO₃(s), −635 kJ mol⁻¹ for CaO(s) and −394 kJ mol⁻¹ for CO₂(g), calculate ΔH for CaCO₃(s) → CaO(s) + CO₂(g).
Model answer
The products total −1029 kJ mol⁻¹ and the reactant is −1207 kJ mol⁻¹, so ΔH is −1029 minus −1207, which is +178 kJ mol⁻¹.
- 6
Using ΔfHӨ values of +52 kJ mol⁻¹ for C₂H₄(g), −286 kJ mol⁻¹ for H₂O(l) and −278 kJ mol⁻¹ for C₂H₅OH(l), calculate ΔH for C₂H₄(g) + H₂O(l) → C₂H₅OH(l).
Model answer
The reactants total +52 − 286, which is −234 kJ mol⁻¹, so ΔH is −278 minus −234, which is −44 kJ mol⁻¹.
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