EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:2.7.3 Tests for Cations

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:2.7.3 Tests for Cations

Tests for Cations

 

 

  • Metal cations in aqueous solution can be identified by the colour of the precipitate they form on addition of sodium hydroxide and ammonia
  • If only a small amount of NaOH is used then normally the metal hydroxide precipitates

 

 Analysing results

  • The table below contains the results for each of the cations included in the syllabus
  • If a precipitate is formed from NaOH then the hydroxide is insoluble in water

 

Testing for Cations Table

 

 

 

 

 

Exam Tip

Sometimes you may not see much of a precipitate because the cation you are testing is present is very small amounts. However, every a slight cloudiness or colour change can indicate a positive test result.

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