Key term
Edexcel A-Level Chemistry 9CH0
Atomic Structure and the Periodic Table
Bonding and Structure
Inorganic Chemistry and the Periodic Table
Topic overviewFlame tests and how they workThermal decomposition of nitrates and carbonatesCarrying out flame tests and testing the gasesGroup 2 elements and their compoundsTrends in Group 7 and predicting fluorine and astatineHalogen displacement reactionsDisproportionation and the reactions of chlorineHalides with concentrated sulfuric acid, and the hydrogen halidesTesting for halide ions with silver nitrateTesting for carbonate and hydrogencarbonate ionsTesting for sulfate and ammonium ions
Formulae, Equations and Amounts of Substance
Topic overviewThe mole, molar mass and empirical formulaThe ideal gas equation and molar volumeEquations, concentration and reacting quantitiesStandard solutions, titration and uncertaintyPercentage yield, atom economy and acid reactionsCore practicals 1 to 3Empirical formula and water of crystallisation by experimentApparatus, uncertainty and mathematical skills
Organic Chemistry I
Topic overviewFormulae, homologous series and functional groupsIUPAC nomenclatureTypes of organic reaction and structural isomerismStereoisomerism and E/Z nomenclaturePractical techniques in organic chemistryAlkanes, crude oil and combustion pollutantsRadical substitutionAlkenes, the double bond and hydrogenationElectrophilic addition, Markovnikov's rule and the test for an alkeneAddition polymers and waste polymersNucleophilic substitution of halogenoalkanesRates of hydrolysis and the SN1 and SN2 mechanismsClassifying and oxidising alcoholsAlcohols: practical techniques and the core practicals
Modern Analytical Techniques I
Energetics I
Kinetics I
Equilibrium I
Acid-Base Equilibria
Energetics II
Redox II
Transition Metals
Topic overviewElectron configuration and what makes a transition metalComplex ions, ligands and the colour of transition metal ionsCoordination number, monodentate ligands and the shapes of complexesBidentate and multidentate ligands, and ligand exchangeVanadium and chromium chemistryReactions with sodium hydroxide and ammoniaCobalt and copper complexesLigand exchange, amphoteric behaviour and the chelate effectTransition metals as catalysts
Kinetics II
Organic Chemistry II
Topic overviewChiralityAldehydes, ketones and their oxidationReduction and nucleophilic addition of HCNTesting for a carbonyl group: 2,4-DNPH and the iodoform reactionCarboxylic acids and their reactionsEsters and acyl chloridesReflux, extraction and recrystallisationDistillation, melting temperature and working safely
Organic Chemistry III
Topic overviewThe structure of benzene and the evidence for itElectrophilic substitution of benzeneNitration, halogenation, Friedel-Crafts and phenolAmines: structure and basicityReactions of amines and preparing themAmides and condensation polymersAmino acids, zwitterions and proteinsEmpirical and molecular formulae from analytical dataGrignard reagents and multi-step synthesisPurification techniques and the aspirin preparation
Acid-Base Equilibria
Calculating pH, and titration curves
- 3 things to know
- Papers 1 and 3
Overview
Recall questions on the pH of strong and weak acids and of alkalis, on the effect of dilution, and on the four titration curve shapes and their indicators.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
State the expression used to calculate Kₐ from the measured pH and initial concentration of a weak acid.
Key term
What quantities are plotted on the axes of a titration curve?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why does an equimolar solution of a strong acid have a lower pH than an equimolar solution of a weak acid?
Model answer
Because the strong acid is fully dissociated, producing a higher hydrogen ion concentration.
- 2
Why does an equimolar solution of a strong base have a higher pH than an equimolar solution of a weak base?
Model answer
Because the strong base is fully dissociated, producing a higher hydroxide ion concentration and therefore a lower hydrogen ion concentration.
- 3
Dilute a strong acid tenfold — how far does the pH move?
Model answer
The pH increases by 1 unit.
- 4
Diluted tenfold, why does a weak acid's pH shift by under one unit?
Model answer
Because the equilibrium shifts to the right to produce more hydrogen ions, partially compensating for the dilution.
- 5
State the expression used to calculate Kₐ from the measured pH and initial concentration of a weak acid.
Model answer
Kₐ = (10⁻ᵖᴴ)² / [HA]₀
- 6
What quantities are plotted on the axes of a titration curve?
Model answer
pH is plotted on the vertical axis and volume of titrant added is plotted on the horizontal axis.
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