Chemistry - tests

Detecting gases - CO2

• CO2 + limewater

• should create white cloudy precipitate

Detecting gases - chlorine

• Place damp litmus paper above the unknown substance

• If chlorine present litimus paper will bleach white

Detecting gases - hydrogen

• lighted splint over the mouth of a container of gas

• If hydrogen present, the splint will make a squeaky pop sound

Detecting gases - oxygen

• glowing splint over the mouth of a container of gas

• If oxygen present, the splint will relight

Detecting cations - flame test (part 1)

• clean nichrome wire loop by dipping into hydrochloride acid

• Dip nichrome wire loop into power/solution of sample and hold over Busen burner flame

• Record the colour produced

• Repeat all steps for all different samples

Nichrome loop used because it is inert

Detecting cations - flame test (part 2)

lithium - red

Sodium - yellow

Potassium- purple/lilac

Calcium - orangey red

Copper - greeny blue

Detecting cations - hydroxide precipitate test

• mix sodium hydroxide with unknown metal solution

  iron (2) - green

  iron (3) - orangey brown

  copper (3) - blue

  calcium - white

  zinc - white

Detecting ions - carbonate ions

• take unknown substance and react with dilute hydrochloric acid

• If carbonate ions present then bubbles of carbon dioxide should be produced (you can check if co2 present using limewater)

Detecting ions - Sulfate ions

• add unknown substance to tube and add barium chloride solution

• If white precipitate forms, Sulfate ions present

Detecting ions - halide ions

• add unknown substance to tube and add silver nitrate solution

  chloride - white

  bromide - cream

  iodide - yellow