AQA GCSE Science CHEMISTRY Unit C2.6 Acids, bases and salts

• Know that soluble salts can be made from acids and insoluble salts can be made from solutions of ions.

• Know that when acids and alkalis react the result is a neutralisation reaction.

• You should be able to use your skills, knowledge and understanding to select an appropriate method for making a salt, given appropriate information.

AQA GCSE Science CHEMISTRY Unit C2.6.1 Making salts

• a) Know the state symbols in equations are (s), ( l ) , (g) and (aq).

• b) Know that soluble salts can be made from acids by reacting them with:

  • metals – not all metals are suitable; some are too reactive and others are not reactive enough

  • insoluble bases – the base is added to the acid until no more will react and the excess solid is filtered off

  • alkalis – an indicator can be used to show when the acid and alkali have completely reacted to produce a salt solution.

    • You need to be able to suggest methods to make a named soluble salt.

• c) Know that salt solutions can be crystallised to produce solid salts.

• d) Know that insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed.

  • You should be able to name the substances needed to make a named insoluble salt.

  • Know that precipitation can be used to remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent.

AQA GCSE Science CHEMISTRY Unit C2.6.2 Acids and bases

• a) Metal oxides and hydroxides are bases.

  • Soluble hydroxides are called alkalis.

• b) The particular salt produced in any reaction between an acid and a base or alkali depends on:

  • the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)

  • the metal in the base or alkali.

• c) Ammonia dissolves in water to produce an alkaline solution.

  • It is used to produce ammonium salts.

  • Ammonium salts are important as fertilisers.

• d) Hydrogen ions, H⁺(aq), make solutions acidic and hydroxide ions, OH^–(aq), make solutions alkaline.

  • The pH scale is a measure of the acidity or alkalinity of a solution.

  • You should be familiar with the pH scale from 0 to 14, and that pH 7 is a neutral solution.

• e) In neutralisation reactions, hydrogen ions react with hydroxide ions to produce water.

  • This reaction can be represented by the equation:

    • H⁺(aq) + OH^–(aq) ==> H₂O(l)

• Revise demonstrations you saw or practical work you did to develop skills and understanding which may have included the following:

  • the preparation of soluble salts:

    • - copper sulfate by adding copper oxide to sulfuric acid

    • - magnesium sulfate by adding magnesium oxide to sulfuric acid

    • - copper chloride by adding copper oxide to hydrochloric acid

    • - zinc nitrate by adding zinc oxide to nitric acid

    • - sodium chloride by adding sodium hydroxide to hydrochloric acid

    • - copper sulfate by adding copper carbonate to sulfuric acid

    • and investigation of the effect of conditions on the yield of the salt

  • the preparation of insoluble salts:

    • - lead iodide by mixing solutions of lead nitrate and potassium iodide

    • - barium sulfate by mixing solutions of barium chloride and sodium sulfate

    • and investigation of the effect of conditions on the formation of precipitates.

• There are opportunities here for using pH sensors to investigate neutralisation.

• AQA GCSE Additional Science CHEMISTRY

• When revising, these pages provide you with a summary of what you need to know and be able to do.

• BUT remember, your primary source of revision are your class notes, investigations and AQA GCSE science textbooks.

• Revision notes and quizzes to help you revise

  • pH scale, indicator colours, ionic theory of acids, alkalis (bases) & neutralisation

  • Reactions of acids with metals/oxides/hydroxides/carbonates and neutralisation reactions

  • Reactions of bases-alkalis like sodium hydroxide

  • Methods of making salts