1. AS Chemistry cation identification tests a visual guide
Designed by Samuel Millar

2. suspected aqueous cation
KEY
suspected aqueous cation
(colour indicated)
precipitate
solution
smoke
reagent
solution: {
NaOH (aq) sodium hydroxide solution
NH3 (aq) ammonium hydroxide solution
KSCN(aq) potassium thiocyanate solution
K2CrO4 (aq) potassium chromate solution

3. deep blue soln (complex ion solution)
COPPER (II)
NH3 (aq) (add dropwise)
Cu2+(aq)
NaOH (aq)
Cu2+(aq)
pale blue ppt
soluble in excess:
deep blue soln (complex ion solution)
pale blue ppt
insoluble in excess

4. (complex ion solution)
IRON (III)
NH3 (aq) or
NaOH (aq)
Fe3+(aq)
KSCN (aq)
Fe3+(aq)
rust-brown ppt
insoluble in excess
blood red soln
(complex ion solution)

5. IRON (II) Fe2+(aq) NH3 (aq) NaOH (aq) dirty green pptor
NaOH (aq)
Fe2+(aq)
dirty green ppt
insoluble in excess

6. soluble in hydrochloric acid:
BARIUM (II)
KCrO4 (aq)
Ba2+(aq)
yellow ppt
soluble in hydrochloric acid:
yellow soln

7. pungent colourless gas evolved
AMMONIUM
NaOH(aq)
NH4+(aq)
HEAT
pungent colourless gas evolved
reacts with hydrogen chloride vapour:
white smoke

8. soluble: colourless soln insoluble insoluble
ALUMINIUM (III), ZINC (II), MAGNESIUM (II) These cations all produce white precipitates with NaOH and NH3 solutions. The precipitates have the following solubilities in excess:
Al3+ (aq)
Zn2+ (aq)
Mg2+ (aq)
NH3
(aq)
soluble: colourless soln
(complex ion soln)
insoluble
insoluble
NaOH
(aq)
soluble: colourless soln
(ppt amphoteric)
soluble: colourless soln
(ppt amphoteric)
insoluble

9. FLAME TESTS Cation Flame colour Li+ Crimson-red Na+ Yellow/orange K+
Lilac/pink through blue glass
Ca2+
Brick red
Sr2+
Red
Ba2+
Green
Cu2+
Blue-green
Burning glass
Orange!