Chemistry C3: Chemical Detection

Flame Test-Compound want to know what’s in it:

· Sodium: Yellow

· Potassium: Lilac

· Calcium: Brick Red

· Copper: Blue-Green ♫ S, P, C, C, yellow, lilac red and green!!! ♫

Coloured Precipitate-Add Sodium Hydroxide: Many metal hydroxides = insoluble and precipitate out of solution, coloured.

Metal Colour of Precipitate Ionic Reaction

Calcium, Ca²+ White Ca²+(aq) + 20H-(aq) → Ca(OH) ₂(s)

Copper(II), Cu²+ Blue Cu²+(aq) + 20H-(aq) → Cu(OH)₂(s)

Iron(II), Fe²+ Sludgy Green Fe²+(aq) + 20H-(aq) → Fe(OH)₂(s)

Iron(III) Fe³+ Reddish Brown Fe³+(aq) + 30H-(aq) → Fe(OH)₃(s)

Aluminium, Al³+ White then redissolves Al³+(aq) + 30H-(aq) → Al(OH)₃(s)

→ colourless Then Al(OH)₃(s) + 0H- → Al(OH)₄-(aq)

Ammonium, NH₄+ No precipitate but smells

of NH4+

♫Cool women catch birds in gross icky round arched cottages♫

Hydrochloric Acid - Detects Carbonates and Sulphites