Chem 5 colours

the inorganic ions in solution colours

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  • Created by: Ella Shaw
  • Created on: 17-06-12 11:08


[Co(H2O)6]+2: pink solution

Addition of CO3-2: CoCO3- pink precipitate

Addition of dropwise ammonia: Co(H2O)4(OH)2- blue precipitate

Addition of excess or conc. ammonia: [Co(NH3)6]+2- straw coloured solution which oxidises to 3+ which is a brown solution in H2O2 or air

Addition of HCl: [Co(Cl)4]-2- blue solution

Addition of NaOH: Co(H2O)4(OH)2- blue precipitate

Colours of Cobalt: pink, blue, straw coloured, brown

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[Cu(H2O)6]+2: Blue solution

Addition of CO3-2: CuCO3- green-blue precipitate

Addition of dropwise ammonia: Cu(H2O)4(OH)2- blue precipitate

Addition of excess or conc ammonia: [Cu(NH3)4(H2O)2]+2- Royal blue solution

Addition of HCl: [Cu(Cl)4]-2- yellow-green solution

Addition of NaOH: Cu(H2O)4(OH)2- blue precipitate

Colours of Copper: Blue, green-blue, royal blue, yellow-green

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[Cr(H2O)6]+3: Ruby solution (looks green)

Addition of CO3: Cr(OH)3(H2O)3 + CO2- Green precipitate and fizzing/effervesence 

Addition of dropwise ammonia: Cr(OH)3(H2O)3- green precipitate

Addition of excess or conc ammonia: [Cr(NH3)6]+3- purple solution

Addition of dropwise NaOH: Cr(OH)3(H2O)3- green precipitate (amphoteric)

Addition of excess NaOH or KOH: [Cr(OH)6]-3- green solution

Addition of zinc/HCl: [Cr(H2O)6]+2- blue solution

Addition of KOH, H2O2: CrO4-2- yellow solution which goes to Cr2O7-2 orange solution when H+ ions are added

Colours of Chromium: Ruby (looks green), green, purple, blue, yellow, orange

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Fe2+ (colours pale green, green)

[Fe(H2O)6]+2: pale green solution which with addition of air/H2O2 goes to [Fe(H2O)6]+3- violet solution (looks yellow-brown)

Addition of dropwise and excess ammonia and NaOH: Fe(H2O)4(OH)2 green precipitate which oxidises to Brown precipitate Fe(H2O)3(OH)3 with O2 in air

Addition of CO3: FeCO3- green precipitate

Fe3+ (colours brown, violet (looks yellow-brown))

[Fe(H2O)6]+3- violet solution (looks yellow-brown) with addition of zinc and HCl goes to [Fe(H2O)6]+2: pale green solution 

Addition of dropwise and excess ammonia and NaOH: Fe(H2O)3(OH)3- brown precipitate

Addition of CO3: Fe(OH)3(H2O)3 + CO2- brown precipitate and effervesence

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[Al(H2O)6]+3: colourless solution

Addition of ammonia: Al(OH)3(H2O)3- white precipitate

Addition of CO3: Al(OH)3(H2O)3 + CO2- white precipitate and effervesence

Additon of dropwise NaOH: Al(OH)3(H2O)3- white precipitate

Addition of excess NaOH: [Al(OH)4]- 

Colours of Aluminium: colourless, white

AL(OH)3(H2O)3 is amphoteric 

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Rules for writing half equations

Under alkaline condiitons: write the formulae for reactant and product, work out the change in oxidation state and add in electrons, add OH- ions to balance charge, add water molecules to balance hydrogen atoms. if that doesnt work then write the hald equation as if it was acidic, remove H+ ions by adding OH- ions to both sides which forms water molecules, simplify by crossing off species that appear on both sides 

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