Summary Reactions of ions in aqueous solution reaction pathway (inc. colours)

Excess
No further NaOH / Fe(H2O)4(OH)2 (s) NaOH / [Fe(H2O)6]²+(aq) Na2CO3
FeCO3 (s)
change NH3 NH3
green precipitate green solution green precipitate
brown on standing in air
add conc HCl
[FeCl4]2– (aq)
yellow solution


Excess
No further NaOH / Fe(H2O)3(OH)3(s) NaOH / [Fe(H2O)6]3+(aq) Na2CO3
Fe(H2O)3(OH)3(s)
change NH3 NH3
brown precipitate purple solution brown precipitate
(may look orange-brown) may look yellow-brown due to some may look orange-brown due to some
[Fe(H2O)5(OH)]2+(aq) [Fe(H2O)5(OH)]2+(aq)
add conc HCl
[FeCl4]– (aq)
+ CO2 gas
yellow solution


Excess
NH3 Na2CO3
2+
[Cu(H2O)2(NH3)4] (aq) Cu(H2O)4(OH)2(s) NaOH / [Cu(H2O)6]2+(aq) CuCO3(s)
No further NH3
deep blue solution change with blue precipitate blue solution blue - green precipitate
excess NaOH add conc HCl
[CuCl4]2– (aq)
green solution

Excess
-
[Al(OH4) ](aq) NaOH Al(H2O)3(OH)3 (s) NaOH / [Al(H2O)6]3+(aq) Na2CO3
Al(H2O)3(OH)3(s)
No further NH3
colourless solution change with white precipitate colourless solution white precipitate
excess NH3 add conc HCl
[AlCl4]–(aq)
+ CO2 gas
colourless solution