Key term
Eduqas A-Level Chemistry A410QS
Formulae and Equations
Basic Ideas About Atoms
Topic overviewRadioactive decay and nuclear equationsBehaviour of α, β and γ radiationHalf-life and radioactive decay calculationsRadiation hazards and the uses of radioisotopesIonisation energy and its variation between elementsSuccessive ionisation energies and electronic structureOrbitals and electron configurations of elements 1 to 36Emission and absorption spectraThe hydrogen spectrum, E = hf and the convergence limit
Chemical Calculations
Topic overviewRelative atomic, isotopic, formula and molecular massPrinciples of the mass spectrometerMass spectra, isotopic abundance and relative atomic massEmpirical and molecular formulaeThe mole, the Avogadro constant and molar massMoles, grams and numbers of particlesConcentration and solubilityMolar volume and gas volume correctionsThe ideal gas equationStoichiometry and reacting quantitiesAcid-base titration calculationsAtom economy, percentage yield and percentage error
Bonding
Solid Structures
The Periodic Table
Topic overviewArrangement of the elements and the s-, p- and d-blocksOxidation and reduction as electron transferTrends across periods and down groupsReactions of Group 2 elements with oxygen, water and steamReactions of the aqueous cations Mg²⁺, Ca²⁺ and Ba²⁺Flame coloursReactivity of Group 1 and Group 2 metalsThermal stability of the Group 2 carbonates and hydroxidesSolubility of the Group 2 hydroxides and sulfatesBasic character of the Group 1 and Group 2 oxides and hydroxidesVolatility of the halogens and their reactions with metalsOxidising power, displacement reactions and the silver nitrate testWater treatment, salt preparation and gravimetric analysis
Simple Equilibria and Acid-Base Reactions
Thermochemistry
Rates of Reaction
The Wider Impact of Chemistry
Organic Compounds
Hydrocarbons
Topic overviewAlkanes and the sigma-bonded frameworkCombustion of alkanes and the use of fossil fuelsFree radical substitution and the photochlorination of alkanesAlkenes and the reactivity of the C=C bondE–Z isomerismElectrophilic addition of bromine to alkenesTests for alkenesMarkovnikov addition of hydrogen bromide and carbocation stabilityCatalytic hydrogenation of alkenesAddition polymerisation
Halogenoalkanes
Topic overviewNucleophilic substitution of primary halogenoalkanesElimination reactions forming alkenesBond polarity, bond enthalpy and the ease of substitutionThe silver nitrate test for halogenoalkanesUses of halogenoalkanes and the regulation of their useCFCs and their effect in the upper atmosphereHeating under reflux
Alcohols and Carboxylic Acids
Topic overviewIndustrial preparation of ethanol from etheneFermentation and the distillation of ethanolBiofuels and the issues they raiseClassifying alcohols as primary, secondary and tertiaryDehydration of alcohols to alkenesOxidation of primary alcohols to aldehydes and carboxylic acidsOxidation of secondary alcohols to ketonesThe dichromate(VI) test for alcoholsCarboxylic acids and the sodium hydrogencarbonate testReactions of carboxylic acids with bases, carbonates and hydrogencarbonatesEsterification and separation by distillation
Instrumental Analysis
Redox and Standard Electrode Potential
Redox Reactions
Chemistry of the P-Block
Topic overviewAmphoteric behaviour of aluminium and leadThe inert pair effect in Groups 3, 4 and 5Electron-deficient compounds and expanded octetsAl₂Cl₆ and donor-acceptor compoundsHexagonal and cubic boron nitrideStability of oxidation states II and IV in Group 4Carbon dioxide and lead(II) oxideBonding in the Group 4 chloridesHydrolysis of the Group 4 chloridesReactions of aqueous lead(II) ionsChlorine with cold and warm aqueous sodium hydroxideBleaching and bactericidal action of chlorine and chlorate(I)Sodium halides with concentrated sulfuric acid
Chemistry of the D-Block Transition Metals
Topic overviewOxidation states of the d-block elementsImportant oxidation states and the colours of aqueous ionsBonding in tetrahedral and octahedral complexesThe origin of colour and the splitting of d-orbitalsLigand exchange and change of coordination numberColours and formulae of copper and cobalt complex ionsHeterogeneous and homogeneous catalysisNickel in hydrogenation and iron in the Haber processVanadium(V) oxide and manganese(IV) oxide as catalystsReactions of Cr³⁺, Fe²⁺, Fe³⁺ and Cu²⁺ with excess aqueous hydroxide
Chemical Kinetics
Enthalpy Changes for Solids and Solutions
Entropy and Feasibility of Reactions
Equilibrium Constants
Acid-Base Equilibria
Topic overviewThe Lowry–Brønsted theory and conjugate pairsStrong and weak acids and the dissociation constant KaThe ionic product of water, KwpH of strong acids and strong basespH of weak acids from Ka and pKaTitration curvesHow buffer solutions workBuffer calculationsBuffers in living systems and industrySalt hydrolysis and the choice of indicator
Stereoisomerism
Aromaticity
Alcohols and Phenols
Aldehydes and Ketones
Topic overviewPreparing aldehydes and ketones by oxidation of alcoholsDistinguishing aldehydes and ketones with Tollens’ reagent and Fehling’s solutionReduction of aldehydes and ketones using NaBH₄Nucleophilic addition of HCN to aldehydes and ketonesReaction with 2,4-dinitrophenylhydrazineThe triiodomethane (iodoform) test
Carboxylic Acids and Their Derivatives
Topic overviewRelative acidity of carboxylic acids, phenols, alcohols and waterPreparing carboxylic acids by oxidationReduction and decarboxylation of carboxylic acidsAcid chlorides and their reactionsEsters and their hydrolysisAmides and their hydrolysisNitriles from carboxylic acids and halogenoalkanesHydroxynitriles, hydrolysis and reduction of nitriles
Amines
Amino Acids, Peptides and Proteins
Organic Synthesis and Analysis
Topic overviewPlanning a multi-step synthesisChoosing between alternative routesManipulation and separation techniquesPurification and melting temperatureAddition and condensation polymerisationPolyesters and polyamidesHigh resolution proton NMRCombining spectra to elucidate a structureInterpreting chromatographic dataGas chromatography and HPLC
Specified Practical Work
Topic overviewGravimetric analysis and qualitative analysis of unknown solutionsStandard solutions, standardising an acid and preparing a soluble saltBack titration and double titrationDetermining enthalpy changes by calorimetryFollowing a rate by gas collection, the iodine clock and reaction orderElectrochemical cells, redox titration and the estimation of copperDetermining an equilibrium constant and following a titration with a pH probeHydrolysis of 1-bromobutane and the preparation of an esterOrganic synthesis, purification and identification
Practical Skills and Techniques
Topic overviewChoosing apparatus and recording measurementsVolumetric technique with pipette, burette and volumetric flaskTitration procedure and the choice of indicatorHeating, heating under reflux and distillationFiltration, purification and qualitative testingMelting temperature, chromatography and electrochemical cellsVariables, errors and risk in evaluating a method
Mathematical Skills in Chemistry
Topic overviewStandard form, units and significant figuresRatios, fractions and percentagesChanging the subject and substituting valuesLogarithms, pH and pKaExponentials, the Arrhenius equation and rateGraphs, gradients and interceptsTangents and rates of changeArea under a curveUncertainty and combining errorsThe gas equation and equilibrium expressions
Acid-Base Equilibria
- 10 subtopics
- 29 things to know
- Component 1
What Acid-Base Equilibria covers
Acid-Base Equilibria is examined in Component 1, Physical and Inorganic Chemistry, and drawn on again in Component 3. It covers the Lowry–Brønsted theory and conjugate pairs, strong and weak acids and the dissociation constant Ka, the ionic product of water, Kw, pH of strong acids and strong bases, pH of weak acids from Ka and pKa, titration curves, how buffer solutions work, buffer calculations, buffers in living systems and industry and salt hydrolysis and the choice of indicator.
Where it is assessed
Component 1
Physical and Inorganic Chemistry, and drawn on again in Component 3.
Check the Eduqas specification ↗The 10 subtopics
Each one has its own page.
- The Lowry–Brønsted theory and conjugate pairsConjugate acid-base pair, conjugate base of hydrogen chloride and conjugate acid of ammonia.Open →
- Strong and weak acids and the dissociation constant KaRecall questions on the meaning of Ka and pKa and the relationship between them, why no Ka is quoted for a strong acid, comparing two acids from their Ka values or their pH at equal concentration, and why dilution increases the degree of dissociation of a weak acid.Open →
- The ionic product of water, KwRecall questions on the definition and value of Kw, why the concentration of water is omitted, the relationship between the hydrogen and hydroxide ion concentrations, the pH of pure water, and why that pH falls below seven as the temperature rises although the water stays neutral.Open →
- pH of strong acids and strong basesRecall questions on calculating the pH of a strong monoprotic and a diprotic acid from its concentration, calculating the pH of a strong base through Kw, working backwards from a pH to a concentration, and the effect of a tenfold dilution on the pH.Open →
- pH of weak acids from Ka and pKaRecall questions on the Ka expression and the approximations used, calculating the pH of a weak acid from its Ka and concentration, working back from a measured pH to Ka, the relationship between pH and pKa at half neutralisation, and when the approximations break down.Open →
- Titration curvesEquivalence point of a titration, half-equivalence point of a weak acid titration and why the pH equals the pKa at the half-equivalence point.Open →
- How buffer solutions workBuffer solution, acidic buffer mixture and capacity of a buffer.Open →
- Buffer calculationsRecall questions on the buffer expression and why it uses the ratio of acid to salt, calculating the pH of a buffer from stated amounts, working from an acid partly neutralised by alkali, finding the ratio needed for a target pH, and the effect of adding a small amount of acid or alkali.Open →
- Buffers in living systems and industryNormal pH range of human blood, principal buffer system of blood plasma and how the blood buffer copes with acid entering the bloodstream.Open →
- Salt hydrolysis and the choice of indicatorHydrolysis of a salt, substance is an acid-base indicator and rule for choosing a suitable indicator for a titration.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Identify the conjugate base of hydrogen chloride.
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Write the equation for the ionisation of water.
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Explain why the hydrogen ion concentration of a strong monobasic acid can be taken as its stated concentration.
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State the expression used to find the hydrogen ion concentration of a weak acid.
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Which two components are needed to make an acidic buffer?
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State the expression used to find the hydrogen ion concentration of an acidic buffer.
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Name the principal buffer system of blood plasma.
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Write the equation for the hydrolysis of the ammonium ion.
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Identify the conjugate acid of ammonia.
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Write the expression for the acid dissociation constant of a weak acid HA.
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Write the expression for the ionic product of water.
Numbers
Calculate the pH of 0.0500 mol dm⁻³ hydrochloric acid.
Numbers
Calculate the pH of 0.100 mol dm⁻³ ethanoic acid, for which Ka is 1.75 × 10⁻⁵ mol dm⁻³.
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What quantities are plotted on the two axes of a titration curve?
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Give an example of an acidic buffer mixture.
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State the logarithmic form of the expression used for buffer calculations.
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Write the equilibrium that operates in the blood buffer system.
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Write the equation for the hydrolysis of the ethanoate ion.
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Identify the two conjugate pairs in the equilibrium CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺.
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Explain why the concentration of water does not appear in the expression for Ka.
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State the value and units of Kw at 298 K.
Numbers
Calculate the pH of 0.200 mol dm⁻³ nitric acid.
Numbers
Calculate the pH of 0.0500 mol dm⁻³ methanoic acid, for which Ka is 1.60 × 10⁻⁴ mol dm⁻³.
Key term
Describe the shape of the curve obtained when a weak acid is titrated with a weak base.
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Which two components are needed to make a basic buffer?
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Explain why the volume of the solution cancels out of a buffer calculation.
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Explain how the blood buffer copes with acid entering the bloodstream.
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Write the general equilibrium that describes an acid-base indicator.
Take Acid-Base Equilibria further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
What is a conjugate acid-base pair?
Model answer
It is a pair of species that differ by a single proton, the acid becoming the base once it has donated that proton.
- 2
Identify the conjugate base of hydrogen chloride.
Model answer
The chloride ion, Cl⁻.
- 3
Identify the conjugate acid of ammonia.
Model answer
The ammonium ion, NH₄⁺.
- 4
Identify the two conjugate pairs in the equilibrium CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺.
Model answer
CH₃COOH is paired with CH₃COO⁻, and H₃O⁺ is paired with H₂O.
- 5
What is the name of the H₃O⁺ ion?
Model answer
It is the hydroxonium ion, also called the oxonium ion.
- 6
Explain why a bare proton is never found in aqueous solution.
Model answer
A proton is so small and so highly charged that it is immediately bound by a lone pair on a water molecule to form H₃O⁺.
What is inside Levo
Six ways to work the same material.
Acid-Base Equilibria revision questions
- What does Acid-Base Equilibria cover in Eduqas A-Level Chemistry?
- 10 subtopics: the lowry–brønsted theory and conjugate pairs, strong and weak acids and the dissociation constant ka, the ionic product of water, kw, ph of strong acids and strong bases, ph of weak acids from ka and pka, titration curves, how buffer solutions work, buffer calculations, buffers in living systems and industry and salt hydrolysis and the choice of indicator. Each one has its own page with questions and model answers.
- How is Acid-Base Equilibria organised?
- By the Eduqas A410QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Acid-Base Equilibria, 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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