transition metal colours Flashcards
[Cu(H2O)6]2+
pale blue solution
Cu(OH)2
pale blue solution
[Cu(NH3)4(H2O)2]+2
dark blue solution
[CuCl4]2-
yellow solution
[Cr(H2O)6]+3
pale purple solution (violet)
-usually appears green as often contains other mixed complexes of chromium(III) ions
[Cr(H2O)5SO4]+
green solution
Cr(OH)3
grey green precipitate
[Cr(NH3)6}+3
purple
Cu2+ with sodium hydroxide
-blue precipitate, insoluble
Cu2+ +2OH- –> Cu(OH)2
Fe2+ with sodium hydroxide
pale green solution reacts to form a green precipitate (ironIIhydroxide)
-insoluble in excess
Fe2+ + 2OH- –> Fe(OH)2
Fe2+ with air
- turns brown at its surface as is oxidised to form iron(III)
- Fe(OH)2 –> Fe(OH)3
Fe3+ with sodium hydroxide
- pale yellow solution reacts to form an orange brown precipitate
- Fe3+ +3OH- –> Fe(OH)3
- insoluble in excess
Mn2+ with sodium hydroxide
- pale pink solution reacts to form a light brown precipitate of manganese (II) hydroxide which darkens on standing in air
- Mn2+ (aq) + 2OH- (aq) –> Mn(OH)2 (s)
- insoluble in excess
Cr3+ with sodium hydroxide
violet solution reacts to form a grey green precipitate of chromium hydroxide
-Cr3+ +3OH- –> Cr(OH)3
the precipitate is soluble in excess sodium hydroxide forming a dark green solution
-Cr(OH)3 +3OH- –> [Cr(OH)6]3-
Cu(OH)2 with ammonia
-blue precipitate which dissolved in excess ammonia to form a deep blue solution [Cu(NH3)4(H2O)2]2+
Fe2+, Fe3+, Mn2+ react with ammonia
same way as with sodium hydroxide forming precipitate of X(OH)X
-no further reaction so the precipitates don’t dissolve
[Co(H2O)6]2+
pink
[Co(Cl4)]2-
blue
ammonium ions
- when heated with hydroxide ions procured ammonia gas
- NH4+ + OH- –> NH3 + H2O
- should turn damp red PH paper blue
Cu2+
- pale blue solution
- forms blue ppt that is insoluble in excess NaOH
- blue ppt then deep blue solution soluble in excess NH3
Fe2+
- pale green solution
- green ppt, insoluble in excess NaOH
- turns brown in air
- green ppt insoluble in excess NH3
Fe3+
pale yellow solution
- orange/brown ppt, insoluble in excess NaOH
- orange/brown ppt, insoluble in excess NH3
Mn2+
-pale pink solution
light brown ppt that is insoluble in excess NaOH
-light brown ppt insoluble in excess NH3
Cr3+
violet solution but can appear green due to impurities
- grey ppt that IS soluble n excess NaOH and forms a dark green solution
- grey ppt with ammonia that is soluble in excess, dissolving to form a purple solution
