Qualitative Analysis: Cation Identification

Flashcards covering the identification of various cations using aqueous sodium hydroxide and aqueous ammonia based on precipitate formation and solubility.

Aluminium ion ($Al^{3+}+$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a white precipitate of aluminium hydroxide ($Al(OH)_3$); it dissolves in excess to form a colourless solution.

Aluminium ion ($Al^{3+}$) with aqueous ammonia ($NH_3(aq)$)

A few drops form a white precipitate of aluminium hydroxide ($Al(OH)_3$); the precipitate is insoluble in excess.

Zinc ion ($Zn^{2+}$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a white precipitate of zinc hydroxide ($Zn(OH)_2$); it dissolves in excess to form a colourless solution.

Zinc ion ($Zn^{2+}$) with aqueous ammonia ($NH_3(aq)$)

A few drops form a white precipitate of zinc hydroxide ($Zn(OH)_2$); it dissolves in excess to form a colourless solution.

Calcium ion ($Ca^{2+}$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a white precipitate of calcium hydroxide ($Ca(OH)_2$); the precipitate is insoluble in excess.

Calcium ion ($Ca^{2+}$) with aqueous ammonia ($NH_3(aq)$)

No precipitate is observed when adding drops or excess.

Ammonium ion ($NH_4^+$) with aqueous sodium hydroxide ($NaOH(aq)$)

No precipitate is formed. On heating, ammonia gas is given off which turns damp red litmus paper blue.

Ammonium ion ($NH_4^+$) with aqueous ammonia ($NH_3(aq)$)

No change is observed.

Copper(II) ion ($Cu^{2+}$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a light blue precipitate of copper(II) hydroxide ($Cu(OH)_2$); the precipitate is insoluble in excess.

Copper(II) ion ($Cu^{2+}$) with aqueous ammonia ($NH_3(aq)$)

A few drops form a light blue precipitate of copper(II) hydroxide ($Cu(OH)_2$); it dissolves in excess to form a dark blue solution.

Iron(II) ion ($Fe^{2+}$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a green precipitate of iron(II) hydroxide ($Fe(OH)_2$); the precipitate is insoluble in excess and turns brown on standing.

Iron(II) ion ($Fe^{2+}$) with aqueous ammonia ($NH_3(aq)$)

A few drops form a green precipitate of iron(II) hydroxide ($Fe(OH)_2$); it is insoluble in excess and turns brown on standing.

Iron(III) ion ($Fe^{3+}$) with aqueous sodium hydroxide ($NaOH(aq)$)

A few drops form a red-brown precipitate of iron(III) hydroxide ($Fe(OH)_3$); the precipitate is insoluble in excess.

Iron(III) ion ($Fe^{3+}$) with aqueous ammonia ($NH_3(aq)$)

A few drops form a red-brown precipitate of iron(III) hydroxide ($Fe(OH)_3$); the precipitate is insoluble in excess.