Chemical Tests

Test for Hydrogen

Lit splint burns with a squeaky pop

Oxygen

Glowing splint relights

Carbon Dioxide

Bubble through limewater

Limewater turns cloudy/milky

Ammonia

Damp red litmus paper turns blue

Chlorine

Damp blue litmus paper is bleached

How to prepare a metal wire for a flame test

1. Dip a loop of unreactive metal wire into concentrated acid

2. Hold it in the blue flame Bunsen burner until no colour change

   1. this cleans wire loop + avoids contamination

3. Dip wire loop into solid metal sample

4. Place wire into blue flame of Bunsen burner

   1. avoid getting wire too hot => glows red => confused colour

Flame Test Colour: Lithium

Red

Flame Test Colour: Sodium

Yellow

Flame Test Colour: Potassium

Lilac

Flame Test Colour: Calcium

Orange-red

Flame Test Colour: Copper

Blue-green

Test for Cations (metal ions)

Identified by colour of the precipitate they form with an addition of NaOH

Cation Test: Ammonium

Ammonia gas formed

=> damp red litmus paper turns blue

Cation Test: Copper (II)

Light blue precipitate

Cation Test: Iron (II)

Green precipitate

Cation Test: Iron (III)

Red-brown precipitate

Test for Anions (non-metal ions)

Dilute nitric acid + aqueous silver nitrate (or barium nitrate - SO4)

Anion Test: Chloride Ion

Dilute nitric acid + aqueous silver nitrate

=> white precipitate

Anion test: Bromide Ion

Dilute nitric acid + aqueous silver nitrate

=> cream precipitate

Anion Test: Iodide Ion

Dilute nitric acid + aqueous silver nitrate

=> yellow precipitate

Anion Test: Sulphate Ion

Dilute nitric acid + aqueous barium nitrate

=> white precipitate

Anion Test: Carbonate Ion

Add dilute acid + test gas produced

=> CO2 produced (effervescence)

Chemical Test for H2O

Anhydrous copper sulphate + water

=> white → blue

Physical Test for H2O

Check boiling point with thermometer

=> boils at exactly 100°C