(8) 20 questions

• How can you test for hydrogen gas?

  squeaky pop with lit splint
• How can you test for oxygen gas?

  re-light a glowing splint
• How can you test for carbon dioxide gas?

  limewater turns cloudy
• How can you test for chlorine gas?


  litmus paper bleaches
• How do you calculate the Rf value of a substance?

  distance moved by substance / distance moved by solvent
• What is the mobile phase in chromatography?

  water / solvent
• What is the stationary phase in chromatography?

  paper
• What is a pure substance?

  single element or compound
• What is a formulation?

  a mixture to make a useful substance
• How can you test if a substance is pure? 


  it has a specific boiling / melting point
• Give four advantages of instrumental methods of analysis.

  very fast, very sensitive, accurate, can be used on small samples
• What type of substances can be analysed using flame spectroscopy?

  solutions containing metal ions
• What colour flame is produced when a sample of copper chloride is used in a flame test?

  green
• What is a precipitate?


  a solid formed when two liquids are mixed together
• What colour is a copper(II)hydroxide precipitate?

  blue
• How can a sulfate be identified?

  when you add hydrochloric acid - a white precipitate is formed
• What colour is a precipitate of silver bromide?

  cream
• In chromatography what does the Rf value depend on?

  how soluble the solute is in the solvent
• In chromatography, why must the line that the substances are placed on, be drawn in pencil?

  pencil doesn't dissolve into the solvent
• In chromatography why must the solvent height be lower than the pencil line?

  so that the substances don't dissolve into the solvent off the paper