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
Lattice Enthalpy, Entropy and Free Energy
Standard entropy change calculations
- 3 things to know
- Unit A2 1
Overview
Recall questions on the products-minus-reactants expression and why coefficients are applied, worked calculations for the decomposition of calcium carbonate, the synthesis of ammonia, boiling water and the reduction of carbon dioxide, converting to kJ K⁻¹ mol⁻¹, why an element's standard entropy is not zero, and why boiling gives a far larger change than melting.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Why must each standard entropy be multiplied by the coefficient from the balanced equation?
Numbers
Calculate ΔSӨ for CaCO₃(s) → CaO(s) + CO₂(g), given standard entropies of 93, 40 and 214 J K⁻¹ mol⁻¹ respectively.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the expression used to calculate a standard entropy change for a reaction.
Model answer
The standard entropy change equals the total standard entropy of the products minus the total standard entropy of the reactants.
- 2
Why must each standard entropy be multiplied by the coefficient from the balanced equation?
Model answer
Standard entropies are quoted per mole, so a species present as two moles contributes twice its molar value.
- 3
Calculate ΔSӨ for CaCO₃(s) → CaO(s) + CO₂(g), given standard entropies of 93, 40 and 214 J K⁻¹ mol⁻¹ respectively.
Model answer
The products total 40 + 214 = 254 J K⁻¹ mol⁻¹, so ΔSӨ is 254 − 93 = +161 J K⁻¹ mol⁻¹.
- 4
Calculate ΔSӨ for N₂(g) + 3H₂(g) → 2NH₃(g), given standard entropies of 192, 131 and 192 J K⁻¹ mol⁻¹ respectively.
Model answer
The products total 2(192) = 384 J K⁻¹ mol⁻¹ and the reactants 192 + 3(131) = 585 J K⁻¹ mol⁻¹, so ΔSӨ is 384 − 585 = −201 J K⁻¹ mol⁻¹.
- 5
Calculate ΔSӨ for H₂O(l) → H₂O(g), given standard entropies of 70 and 189 J K⁻¹ mol⁻¹.
Model answer
The entropy change is 189 − 70 = +119 J K⁻¹ mol⁻¹.
- 6
Calculate ΔSӨ for 2H₂(g) + O₂(g) → 2H₂O(l), given standard entropies of 131, 205 and 70 J K⁻¹ mol⁻¹ respectively.
Model answer
The products total 2(70) = 140 J K⁻¹ mol⁻¹ and the reactants 2(131) + 205 = 467 J K⁻¹ mol⁻¹, so ΔSӨ is 140 − 467 = −327 J K⁻¹ mol⁻¹.
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