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OCR (A) A-Level
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*Revision Materials and Past Papers* 2.1.1 Atomic structure and isotopes 2.1.2 Compounds, formulae and equations 2.1.3 Amount of substance 2.1.4 Acids 2.1.5 Redox 2.2.1 Electron structure 2.2.2 Bonding and structure 3.1.1 Periodicity 3.1.2 Group 2 3.1.3 The halogens 3.1.4 Qualitative analysis 3.2.1 Enthalpy 3.2.2 Reaction Rates 3.2.3 Chemical equilibrium 4.1 Basic concepts and hydrocarbons 4.1.2 Alkanes 4.1.3 Alkenes 4.2.1 Alcohols 4.2.2 Haloalkanes 4.2.3 Organic synthesis 4.2.4 Analytical techniques 5.1.1 How fast? 5.1.2 How far? 5.1.3 Acids, bases and buffers 5.2.1 Lattice enthalpy 5.2.2 Enthalpy and entropy 5.2.3 Redox and electrode potentials 5.3.1 Transition elements 5.3.2 Qualitative analysis 6.1.1 Aromatic compounds 6.1.2 Carbonyl compounds 6.1.3 Carboxylic acids and esters 6.2.1 Amines 6.2.2 Amino acids, amides and chirality 6.2.3 Polyesters and polyamides 6.2.4 Carbon–carbon bond formation 6.2.5 Organic synthesis 6.3.1 Chromatography and qualitative analysis 6.3.2 Spectroscopy Required Practicals

5.3.1 Transition elements

Ligand substitutionLigands and complex ionsPrecipitation reactionsPropertiesRedox reactions

Precipitation Reactions

Specification Reference Topic 5.3.1 (j)

Quick Notes

  • Reactions of metal–aqua ions in test-tube reactions involve precipitation with characteristic colour changes.
  • For OCR (A) A-level, you are expected to memorise the precipitation reactions for Fe²⁺, Fe³⁺, Cu²⁺, Cr³⁺ and Mn²⁺.

Full Notes

Download a full sheet of metal–aqua ion reactions for OCR (A) here.

Reactions of Metal–Aqua Ions in Test-Tube Reactions

The following precipitation reactions and colour changes are expected for OCR (A) A-level students.

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Matt’s exam tip

Start memorising colour changes early. Use the cover–write–check method weekly – it’s simple, effective, and builds recall over time. The earlier you start, the easier it becomes!

Iron (II), Fe²⁺ Reactions

OCR (A) A-Level Chemistry test-tube reactions for Fe2+ metal–aqua ion showing expected precipitate colour changes.

Iron (III), Fe³⁺ Reactions

OCR (A) A-Level Chemistry test-tube reactions for Fe3+ metal–aqua ion showing expected precipitate colour changes.

Copper (II), Cu²⁺ Reactions

OCR (A) A-Level Chemistry test-tube reactions for Cu2+ metal–aqua ion showing expected precipitate colour changes.

Chromium (III), Cr³⁺ Reactions

OCR (A) A-Level Chemistry test-tube reactions for Cr3+ metal–aqua ion showing expected precipitate colour changes.

Manganese (II), Mn²⁺ Reactions

OCR (A) A-Level Chemistry test-tube reactions for Mn2+ metal–aqua ion showing expected precipitate colour changes.