Key term
OCR GCSE Chemistry A J248
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 structuresNanoparticles: size and surface area to volumeUses and risks of nanoparticulate materials
Global Challenges
Topic overviewExtracting metals by reduction and by electrolysisBiological methods of metal extractionRate against yield in industry, and reaction conditionsThe Haber process and fertiliser productionNitrogen, phosphorus and potassium in agricultureLife cycle assessmentRecycling, and the decisions behind itAlloys, and the corrosion of metalsComparing glass, ceramics, polymers, composites and metalsFunctional groups and homologous seriesPredicting the products of organic reactionsAddition polymerisationCondensation polymerisation, and making a polymerDNA and other natural polymersFractional distillation of crude oilThe fractions, and crude oil as a feedstockDependence on hydrocarbons, and crackingChemical cells and fuel cellsThe 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 overviewConcentration in mol/dm³, and titrationTitration calculations, and the mass of a soluteMolar gas volume and the volumes of gasesTheoretical mass and percentage yieldAtom economy, and choosing a reaction pathwayMeasuring 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
Predicting and Identifying Reactions
Topic overviewGroups 1, 7 and 0, and why they behave as they doTransition metalsPredicting reactivity from the Periodic TableReactivity of metals with water and acidsTests for oxygen, hydrogen, carbon dioxide and chlorineTests for aqueous cations and anionsFlame tests, and identifying metal ionsIdentifying a species from test resultsInstrumental methods of analysis
Predicting and Identifying Reactions
Tests for aqueous cations and anions
- 3 things to know
- Paper 4
Overview
Using sodium hydroxide solution to identify calcium, copper(II), iron(II), iron(III) and zinc ions by their precipitates, telling calcium from zinc with excess reagent, the acid test for carbonate ions, acidified silver nitrate for chloride, bromide and iodide ions, the barium chloride test for sulfate ions, and why acid is added first in the halide and sulfate tests.
What you need to know
Answer each one before you reveal it.
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Key term
Which reagent is added to a solution to test for calcium, copper, iron and zinc ions?
Key term
What is seen when sodium hydroxide solution is added to a solution containing calcium ions?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which reagent is added to a solution to test for calcium, copper, iron and zinc ions?
Model answer
Sodium hydroxide solution, added drop by drop and then in excess.
- 2
What is seen when sodium hydroxide solution is added to a solution containing calcium ions?
Model answer
A white precipitate forms, and it does not dissolve when more sodium hydroxide is added.
- 3
What is seen when sodium hydroxide solution is added to a solution containing copper(II) ions?
Model answer
A blue precipitate forms.
- 4
What is seen when sodium hydroxide solution is added to a solution containing iron(II) ions?
Model answer
A green precipitate forms.
- 5
What is seen when sodium hydroxide solution is added to a solution containing iron(III) ions?
Model answer
A red-brown, rust-coloured precipitate forms.
- 6
What is seen when sodium hydroxide solution is added to a solution containing zinc ions?
Model answer
A white precipitate forms first, and it dissolves in excess sodium hydroxide to give a colourless solution.
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