IGCSE Coordinated Science:Identification of Ion and Gases

IGCSE Coordinated Science: Identification of Ions and Gases

Use the following tests to identify aqueous cations:
Ammonium, copper(II), iron(II), iron(III), and zinc by means of aqueous sodium hydroxide and aqueous ammonia as appropriate.

Ammonium (NH4+): Add dilute sodium hydroxide, then heat gently. If the cation is present, damp red litmus paper turns blue and ammonia gas is released.
Copper (II): Add dilute sodium hydroxide or ammonia solution. If the cation is present, a pale blue precipitate forms. However, as you add more ammonia, the precipitate dissolves, leading to a deep blue solution.

Iron (II): Add dilute sodium hydroxide or ammonia solution. If the cation is present, a pale green precipitate forms.
Iron (III): Add dilute sodium hydroxide or ammonia solution. If the cation is present, a red-brown precipitate forms.
Zinc: Add dilute sodium hydroxide or ammonia solution. If the cation is present, a white precipitate forms.
Use the following tests to identify anions:
Carbonate: Add dilute hydrochloric acid.

Anion is present if bubbles give off gas that turns limewater milky.
Chloride: First, add the same amount of nitric acid as the chloride. Then, add silver nitrate solution. Chloride ions will form a white precipitate if present.
Nitrate: Add sodium hydroxide. Afterwards, add some pieces of aluminum. Nitrate ions are present if ammonia gas is given off.
Sulfate: Add the same amount of dilute hydrochloric acid. Next, add Barium Nitrate solution. A white precipitate will form if Sulfate ions are present.
Use the following tests to identify gases:
Ammonia, NH3: Use damp red litmus paper.

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If ammonia is present, the indicator turns blue.
Carbon Dioxide, CO2: Bubble the suspected Carbon Dioxide sample through limewater. If CO2 is present, limewater becomes cloudy or milky.
Chlorine, Cl2: Hold damp litmus paper in the gas. If chlorine is present, the paper turns white.
Hydrogen, H2: Put the gas in the tube and hold a lighted splint into the tube. If hydrogen is present, the gas burns with a 'squeaky pop'.
Oxygen, O2: Collect the gas in a test tube and hold a glowing splint next to it. If oxygen is present, the splint relights."