Testing for gases
- oxygen - use a glowing splint - splint will relight
- hydrogen - use a burning splint - listen for a squeaky pop
- carbon dioxide - add limewater to a test tube, bubble carbon dioxide into test tube - turns cloudy if CO2 is present
- chlorine - use damp red litmus paper - litmus paper will turn colourless
- ammonia - use red litmus paper - litmus paper will turn blue
Conducting a flame test
- A platinum or nichrome wire is dipped into concentrated hydrochloric acid to remove any impurities.
- nichrome wire is inert (unreactive) and has a high melting point
- The wire is dipped into the salt being tested so some salt sticks to the end.
- The wire and salt are held in a burning bunsen burner flame.
- Observe the colour
Testing for metal ions (flame tests)
- Lithium: red
- Sodium: yellow
- Potassium: lilac
- Calcium: orange-red
- Copper: green
Testing for metal ions using sodium hydroxide
- add sodium hydroxide and it forms these precipitates
- Aluminium: white
- Calcium: white
- Magnesium: white
- Copper(II): blue
- Iron(II): green
- Iron(III): brown
- Zinc: white and dissolves