Metalaqua Ion Colours + Reactions Flashcards
Cu2+ solution - colour
🔵 Blue - [Cu(H2O)6] 2+ 🔵
Fe2+ solution - colour
🟢Green 🟢
[Fe(H2O)6 ]2+
Fe3+ solution colour
🟡Yellow 🟡
[Fe(H2O)6 ]3+
Cr3+ solution colour (chromium)
🟪Violet 🟪
[Cr(H2O)6 ]3+
(But often appears green due to impurities in the solution )
Co 2+ solution colour (cobalt )
🌸Pink 🌸
[Co(H2O)6 ] 2+
Addition of NH3 or NaOH to Metal-Aqua ion solution - reaction type
(NOT EXCESS)
- acid base reaction
- :NH3 or :OH- acts as a base, and accepts a proton from one of the water ligands ( technically acting as a nucleophile)
Addition of NaOH / NH3 to a copper solution : colour change
blue precipitate forms from blue solution
🔵Cu(H2O)4(OH)2🔵 (s)
Addition of NaOH / NH3 to Fe2+ solution : colour change
-green precipitate forms ( which is oxidised upon exposure to air turning brown)
Fe(H2O)4(OH)2 (s)
Addition of NaOH or NH3 to an Fe3+ solution
-brown precipitate forms from yellow solution
Fe(H2O)3(OH)3
Addition of NaOH or NH3 to Cr3+ solution : colour change
- green precipitate forms (from violet solution)
Cr(H2O)3(OH)3 (s)
Addition of NaOH or NH3 to Co2+ solution : colour change
- blue precipitate forms (from pink solution)
Cr(H2O)4(OH)2 (s)
Only transition metal solution to react with excess NaOH? - and reaction type
- Cr3+ solution
- As the Cr(OH)3(H2O)3 chromium hydroxide is amphoteric
- acid base
Addition of excess NaOH to Cr3+ solution : observation
- green precipitate redissolves to give green solution
[Cr(OH)6 ] 3- (aq)
Formed by further acid base reaction
Addition of excess NH3 to metal aqua ions solutions - which ones react and what is the reaction type
- Cu2+ , Cr3+ , Co2+
-Ligand substitution reaction
Addition of excess NH3 to Cu2+ solution
-DARK blue solution forms after blue precipitate redissolves
[Cu(NH3)4(H2O)2 ]2+
(2 Water ligands and 2 OH ligands replaced)
Addition of excess NH3 to Cr3+ solution
Purple solution forms (after green precipitate redissolves)
[ Cr(NH3)6 ]3+
(Given [Cr(H2O)6]3+ is violet it makes sense for [Cr(NH3)6]3+ to be a similar colour)
Addition of excess NH3 to Co2+ solution
Yellow solution forms (after blue precipitate dissolves)
[Co(NH3)6 ]2+
Addition of chloride ions to a Cu2+ solution
-Solution turns yellow
-complex change shape (ligand substitution with significantly larger ligands) than H2O
[CuCl4]2-
Addition of chloride ions to Co2+ solution
-
solution turns blue (from pink)
-cobalt tetrachloride
[CoCl4]2-
Give the equation of the chromate- dichromate equilibrium and state the colour change
2 (CrO4)2- + 2H+ —> (Cr2O7)2- + H2O
(CrO4)2- is yellow - chromate (IV)
(Cr2O7)2- is orange - dichromate (VI)
Colour of V2+
Violet
Colour of V3+
Green
Colour of VO 2+ - where oxidation state or vanadium is +4
Blue
Colour of VO2 + , where the oxidation sate of vanadium is +5
Yellow
Why does substituting monodentate with bi- or multi-dentate ligands increase entropy?
-chelate effect
-A solution with more particles in it is created when you replace the mono-dentate ligands, leading to an increase in entropy e.g
[Cr(H2O)6]3+ + EDTA4- —> [Cr(EDTA]- + 6H2O
Colour of MnO4- (where oxidation state of manganese is +7)
Dark purple
Colour of Mn2+
-pale pink (appears colourless when there’s a low concentration of Mn2+)
When KMnO4 (potassium permanganate) is used as a reducing agent, what is manganese in MnO4- reduced to?
-Mn2+
Give the ionic equation for the reduction of MnO4- to Mn2+
MnO4- + 8H+ + 5e- —-> Mn2+ + 4H2O
Give the ionic equation for the reduction of Cr2O72- to Cr3+
Cr2O7 2- +14H+ + 6e- —-> 2Cr3+ + 7H2O
What type of isomerism is exhibited in octahedral complexes ?
-When there’s 6 individual ligands there can be cos/trans isomerism
-If you have a multidentate (EDTA4- ) or bidentate (ethylenediamine or ethanedioate) you can can optical isomerism
Describe the cistrans isomerism seen in square planar and octahedral complexes
- When the two groups are next to each other (cisters) you have the cis isomer
-when the two groups are opposite each other(transverse to one another) you have the trans isomer
