VERSION 1
Designed by Samuel Millar
NOTES
• Black text – CORE KNOWLEDGE
– Red text – EXCEPTIONS TO THE
PATTERNS
• Grey text – EXTENSION
The colour and formula are given
for the complex formed by each ion
with each • reagent, starting with
the aqueous complex.
In the case of NaOH and NH3,
the hydroxide precipitate produced
is given, followed by the complex
formed (if any) when excess (“xs”) of
the reagent is added.
The colours are named as CCEA
wants them in the exam! The colour
boxes hopefully give some
indication of the actual shade.
Most of the complexes involve six
ligands and so are octahedral.
However, chloride complexes take
tetrahedral
or square planar
shapes.
Copper (II) and Cobalt (II)
• ion
• Cu2+
• Co2+
• aq
• blue soln
[Cu(H2O)6]2+
• pink soln
[Co(H2O)6]2+
• NaOH
• blue ppt
[Cu(OH)2(H2O)4]
insoluble in xs
• blue ppt
[Co(OH)2(H2O)4]
insoluble in xs
• NH3
• blue ppt
[Cu(OH)2(H2O)4]
soluble – deep blue soln
[Cu(NH3)4(H2O)2]2+
• blue ppt
[Co(OH)2(H2O)4]
soluble – yellow soln
[Co(NH3)6]2+
• conc HCl
• yellow-green soln
[CuCl4]2-
• blue soln
[CoCl4]2-
Iron (III) and Iron (II)
• ion
• Fe3+
• Fe2+
• aq
• yellow/orange soln
[Fe(H2O)6]3+ *1
• green soln
[Fe(H2O)6]2+
• NaOH
• rust/brown ppt
[Fe(OH)3(H2O)3]
insoluble in xs
• green ppt*2
[Fe(OH)2(H2O)4]
insoluble in xs
• NH3
• rust/brown ppt
[Fe(OH)3(H2O)3]
insoluble in xs
• green ppt*2
[Fe(OH)2(H2O)4]
insoluble in xs
*2NB: Iron (II) hydroxide slowly
•
• blood-red soln
oxidises to iron (III) hydroxide, so a
2[Fe(SCN)(H2O)5]
rust/brown colour is observed after
some time.
*1[Fe(H2O)6]3+ is actually pale violet. The high charge density on the metal ion causes some
deprotonation and the yellow-orange colour is actually due to [Fe(OH)(H2O)5]2+
SCNthiocyanate
Chromium (III) and Manganese (II)
• ion
• Cr3+
• Mn2+
• aq
• green soln
[Cr(H2O)6]3+
• pink soln
[Mn(H2O)6]2+
• NaOH
• green-blue ppt
[Cr(OH)3(H2O)3]
soluble – green soln
[Cr(OH)6]3-
• white ppt*
[Mn(OH)2(H2O)4]
insoluble in xs
• NH3
• green-blue ppt
[Cr(OH)3(H2O)3]
soluble – violet soln
[Cr(NH3)6]3+
• white ppt*
[Mn(OH)2(H2O)4]
insoluble in xs
• aq
• Chromium (VI)
CrO42-
yellow soln
• Chromium (VII)
Cr2O72-
orange soln
• Chrome alum
KCr(SO4)2
violet crystals
*NB: Manganese (II) hydroxide
slowly oxidises to manganese (III)
oxide, so the white (off-white)
precipitate slowly turns brown/black.
Nickel (II) and Vanadium
• ion
• Ni2+
• aq
• green soln
[Ni(H2O)6]2+
• NaOH
• green ppt
insoluble in xs
[Ni(OH)2(H2O)4]
• NH3
• green ppt
soluble – blue soln
[Ni(OH)2(H2O)4]
[Ni(NH3)6]2+
• conc HCl
• yellow soln
[NiCl4]2-
• edta
• blue soln
[Ni(edta)]2-
• en
• purple soln
[Ni(en)3]2+
• aq
• Vanadium (II) V2+
violet
• Vanadium (IV) VO2+
blue
• Vanadium (III) V3+
green
• Vanadium (III) VO2+
yellow