Reactions of metal ions with bases

Ion: Cr3+

Species in aqueous solution: Violet or green [Cr(H2O)6]3+

With Ammonia Solution: Green Precipitate [Cr(H2O)3(OH)3]

With excess ammonia solution: Precipitate is slightly soluble giving a purple solution containing [Cr(NH3)6]3+

Ion: Mn2+

Species in aqueous solution: Very Pale Pink [Mn(H2O)6]2+

With Ammonia Solution: Off-white precipitate [Mn(H2O)4(OH)2] Turns brown in air, oxidised to MnO2

With excess ammonia solution: Does not Dissolve

Ion: Fe2+

Species in aqueous solution: Pale green [Fe(H2O)6]2+

With Ammonia Solution: Green precipitate [Fe(H2O)4(OH)2] Turns brown in air, oxidised to Fe(OH)3

With excess ammonia solution: Does not dissolve

Ion: Fe3+

Species in aqueous solution: Yellow/Brown [Fe(H2O)6]3+

With Ammonia Solution: Reddish-brown precipitate [Fe(H2O)3(OH)3]

With excess ammonia solution: Does not dissolve

Ion: Cu2+

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

With Ammonia Solution: Pale blue precipitate [Cu(H2O)4(OH)2]

With excess ammonia solution: Dissolves to give a deep blue solution containing [Cu(NH3)4(H2O)2]2+

Ion: Zn2+

Species in aqueous solution: Colourless [Zn(H2O)6]2+

With Ammonia Solution: White precipitate [Zn(H2O)4(OH)2]

With excess ammonia solution: Dissolves to give a colourless solution containing [Zn(NH3)4(H2O)2]2+