Designed by Samuel Millar

KEY

suspected aqueous

cation(colour indicated)

{NaOH (aq) sodium hydroxide solutionNH3 (aq) ammonium hydroxide solutionKSCN(aq) potassium thiocyanate solutionK2CrO4 (aq) potassium chromate solution

reagentsolution:

precipitate

solution

smoke

NH3 (aq)(add dropwise)

Cu2+(aq)

pale blue pptsoluble in excess:

deep blue soln(complex ion solution)

pale blue pptinsoluble in excess

COPPER (II)

NaOH (aq)

Cu2+(aq)

NH3 (aq)or

NaOH (aq)

Fe3+(aq)

rust-brown pptinsoluble in excess

blood red soln(complex ion solution)

IRON (III)

KSCN (aq)

Fe3+(aq)

NH3 (aq)or

NaOH (aq)

Fe2+(aq)

dirty green pptinsoluble in excess

IRON (II)

KCrO4 (aq)

Ba2+(aq)

yellow pptsoluble in hydrochloric acid:

yellow soln

BARIUM (II)

NaOH(aq)

NH4+

(aq)

pungent colourless gas evolvedreacts with hydrogen chloride vapour:

white smoke

AMMONIUM

HEAT

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:

NaOH(aq)

NH3(aq)

Al3+

(aq)Zn2+

(aq)Mg2+

(aq)

soluble: colourless soln

(ppt amphoteric)

soluble: colourless soln

(ppt amphoteric)

soluble: colourless soln

(complex ion soln)

insoluble insoluble

insoluble

FLAME TESTSCation Flame colourLi+ Crimson-redNa+ Yellow/orangeK+ Lilac/pink through blue glassCa2+ Brick redSr2+ RedBa2+ GreenCu2+ Blue-greenBurning glass Orange!