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
Aldehydes and Ketones
Reaction with 2,4-dinitrophenylhydrazine
- 3 things to know
- Component 2
Overview
Words what happens to the two molecules during this reaction, class name of the solid product of this reaction and why the product of this reaction is strongly coloured.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is Brady's reagent made from?
Key term
State the positive result seen when Brady's reagent is added to a suitable compound.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is Brady's reagent made from?
Model answer
It is a solution of 2,4-dinitrophenylhydrazine in methanol acidified with concentrated sulfuric acid.
- 2
State the positive result seen when Brady's reagent is added to a suitable compound.
Model answer
A precipitate forms at once, ranging in colour from yellow through orange to red.
- 3
Which functional group does Brady's reagent detect, and what can a positive result not tell you?
Model answer
It detects the carbonyl group, C=O, of an aldehyde or a ketone, but a positive result does not reveal which of the two classes is present.
- 4
Carboxylic acids and esters also contain a carbon–oxygen double bond. Why do they give no precipitate?
Model answer
In those compounds the carbonyl carbon also carries an oxygen atom whose lone pairs are delocalised onto it, which reduces the δ+ charge so the reagent's nitrogen cannot add to it.
- 5
Name the type of mechanism by which 2,4-dinitrophenylhydrazine reacts with a carbonyl compound.
Model answer
Nucleophilic addition–elimination, which is also called a condensation reaction.
- 6
Describe in words what happens to the two molecules during this reaction.
Model answer
The nitrogen of the —NH₂ group attacks the δ+ carbonyl carbon and adds to it, and a molecule of water is then eliminated, so the carbon–oxygen double bond is replaced by a carbon–nitrogen double bond joining the two parts together.
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