Key term
OCR GCSE Combined Science Chemistry J250
Chemical Reactions
Topic overviewWriting formulae of elements and compoundsBalanced equations, and deducing formulae from ionsState symbols in equationsConservation of mass, and changes of mass in open systemsExothermic and endothermic reactions, and reaction profilesActivation energy and why reactions need itOxidation and reduction in terms of oxygenAcids, alkalis and neutralisationThe ionic equation for neutralisation, and reactions of acidsThe pH scale, acidity and alkalinityMeasuring pH with indicators and pH metersProducts 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 electrolysisLife 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
Particles
Chemical Reactions
Acids, alkalis and neutralisation
- 3 things to know
- Paper 3 (Chemistry)
Overview
The hydrogen ions that acids release and the hydroxide ions in alkalis, common acids and alkalis with their formulae, what neutralisation, a base and an alkali are, naming salts and writing equations such as sodium chloride and copper(II) sulfate, and making a pure dry salt by adding an insoluble base in excess to warm dilute acid.
What you need to know
Answer each one before you reveal it.
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Key term
Which ion is present in every alkaline solution?
Key term
Name three common acids and state the ion they all release in water.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which ion do all acids produce when they dissolve in water?
Model answer
The hydrogen ion, H⁺.
- 2
Which ion is present in every alkaline solution?
Model answer
The hydroxide ion, OH⁻.
- 3
What happens to hydrogen chloride when it dissolves in water?
Model answer
It splits into ions, giving H⁺(aq) and Cl⁻(aq).
- 4
Name three common acids and state the ion they all release in water.
Model answer
Hydrochloric, sulfuric and nitric acids, all of which release hydrogen ions.
- 5
What is an alkali?
Model answer
A base that dissolves in water, giving a solution containing hydroxide ions.
- 6
Name two common alkalis and give their formulae.
Model answer
Sodium hydroxide, NaOH, and potassium hydroxide, KOH.
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