Key term
OCR GCSE Combined Science Chemistry J250
Chemical Reactions
Topic overviewWriting formulae of elements and compoundsBalanced equations, and deducing formulae from ionsIonic equations, and state symbolsThe mole and the Avogadro constantConservation of mass, and changes of mass in open systemsStoichiometry, and calculating reacting massesExothermic and endothermic reactions, and reaction profilesActivation energy, and bond energy calculationsOxidation and reduction, by oxygen and by electronsAcids, alkalis and neutralisationThe ionic equation for neutralisation, and reactions of acidsDilute and concentrated, weak and strongThe pH scale, and hydrogen ion concentrationpH as a factor of ten, and measuring pHProducts at the electrodes, and molten ionic compoundsElectrolysis of aqueous solutionsInert and non-inert electrodes
Elements, Compounds and Mixtures
Topic overviewPurity, and melting point dataRelative formula mass and empirical formulaeFormulations, and separating mixturesPaper and thin layer chromatographyInterpreting chromatograms and Rf valuesChoosing a purification methodMetals and non-metals in the Periodic TableElectron arrangement and position in the Periodic TableIonic, covalent and metallic bonding comparedDot and cross diagrams, and the limits of modelsReactions, electron arrangement and Mendeleev's tableCarbon's four bonds, and the variety of organic compoundsDiamond, graphite, fullerenes and grapheneBond strength, intermolecular forces and predicting stateBulk properties of ionic, molecular and giant structures
Global Challenges
Topic overviewExtracting metals by reduction and by electrolysisBiological methods of metal extractionLife cycle assessmentRecycling, and the decisions behind itFractional distillation of crude oilThe fractions, and crude oil as a feedstockDependence on hydrocarbons, and crackingThe Earth's early atmosphere, and how oxygen developedThe greenhouse effect, and evidence for climate changeEffects of carbon dioxide and methane, and air pollutantsProducing potable water
Monitoring and Controlling Chemical Reactions
Topic overviewMass of solute, concentration and dilution calculationsMeasuring the rate of a reaction, and rate graphsFactors affecting rate, and collision theorySurface area and rateCatalysts and how they workReversible reactions and dynamic equilibriumChanging the conditions of an equilibriumActivation energy, and enzymes as catalysts
Particles
Chemical Reactions
The ionic equation for neutralisation, and reactions of acids
- 3 things to know
- Paper 9 (Chemistry)
Overview
The reaction of hydrogen ions with hydroxide ions common to every neutralisation, spectator ions, what is left at the end point, the products and equations of acids with carbonates and metals, and the limewater test for carbon dioxide.
What you need to know
Answer each one before you reveal it.
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Key term
Write the general equation for neutralisation in solution, with state symbols.
Key term
In terms of ions, what is left in the beaker after an acid has been exactly neutralised by an alkali?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which single reaction is common to every neutralisation that happens in water?
Model answer
Hydrogen ions react with hydroxide ions to form water.
- 2
Write the general equation for neutralisation in solution, with state symbols.
Model answer
H⁺(aq) + OH⁻(aq) → H₂O(l).
- 3
Why is the same general equation used whichever acid and alkali are mixed?
Model answer
In every case only the hydrogen ions and hydroxide ions react; the other ions are left unchanged.
- 4
What happens to the sodium ions and chloride ions when sodium hydroxide neutralises hydrochloric acid?
Model answer
They remain in solution unchanged and stay as the dissolved salt.
- 5
What happens to the number of hydrogen ions in an acid as alkali is added to it?
Model answer
It falls, because the hydrogen ions are removed as water is formed.
- 6
In terms of ions, what is left in the beaker after an acid has been exactly neutralised by an alkali?
Model answer
The ions of the salt dissolved in water, with no hydrogen ions or hydroxide ions left over.
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