AQA Chem5: Transition Metals Colours

Revision notes on the colours of transition metal complexes with water, OH-, NH3 and Na2CO3 from AQA Chem5

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  • Created by: anna
  • Created on: 15-06-13 12:43

Cobalt (II)

 

  • Metal-aqua ion: [Co(H2O)6]2+   pink solution
  • With little OH- or NH3: Co(H2O)4(OH)2   blue-green precipitate
  • With excess OH- : Co(H2O)4(OH)2   blue-green precipitate
  • With excess NH3: [Co(NH3)6]2+  straw coloured solution
  • With Na2CO3: CoCO3   pink precipitate
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Copper (II)

 

  • Metal-aqua ion: [Cu(H2O)6]2+    blue solution
  • With little OH- or NH3: Cu(H2O)4(OH)2   blue precipitate
  • With excess OH-: Cu(H2O)4(OH)2   blue precipitate
  • With excess NH3: [Cu(NH3)6]2+   deep blue solution
  • With Na2CO3: CuCO3   green-blue precipitate 
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Iron (II)

 

  • Metal-aqua ion: [Fe(H2O)6]2+   green solution
  • With little OH- or NH3: Fe(H2O)4(OH)2  green precipitate
  • With excess OH-: Fe(H2O)4(OH)2   green precipitate
  • With excess NH3: [Fe(H2O)4(OH)  green precipitate
  • With Na2CO3: FeCO3   green precipitate
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Aluminium (III)

 

  • Metal-aqua ion: [Al(H2O)6]3+   colourless solution
  • With little OH- or NH3: (Al(H2O)3(OH)3   white precipitate
  • With excess OH-: [Al(H2O)2(OH)4]-   colourless solution
  • With excess NH3: [Al(H2O)2(OH)4]-   colourless solution
  • With Na2CO3:  Al(H2O)3(OH)3   white precipitate
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Chromium (III)

 

  • Metal-aqua ion: [Cr(H2O)6]3+   violet solution
  • With little OH- or NH3: Cr(H2O)3(OH) green precipitate
  • With excess OH-: [Cr(OH)6]3-   green solution
  • With excess NH3: [Cr(NH3)6]3+   purple solution
  • With Na2CO3: Cr(H2O)3(OH)3   green precipitate
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Iron (III)

 

  • Metal-aqua ion: [Fe(H2O)6]3+   yellow solution
  • With little OH- or NH3: Fe(H2O)3(OH)3 brown precipitate
  • With excess OH-: Fe(H2O)3(OH)3   brown precipitate
  • With excess NH3: Fe(H2O)3(OH)3   brown precipitate
  • With Na2CO3: Fe(H2O)3(OH)  brown precipitate
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