chemical analysis

• what is the everyday and chemical definition of pure substance?

  • everyday = a substance with nothing added
  • chemical = a substance containing only one element / compound
• what will a chemically pure substance do?

  melt / boil at a specific temperature
• what will impurities in a sample do?

  • lower melting point and increase melting range
  • increase boiling point and increase boiling range
• what are formulations?


  useful mixtures with a precise purpose, and a precise quantity
• what are some examples of formulations?

  • metal alloys
  • cleaning products
  • medicines
  • food
  • fertilisers
  • cosmetics
  • paints
  • fuels
• what is the test for hydrogen?

  squeaky pop = lit splint into a test tube
• what is the test for oxygen?

  glowing splint = relight with a glowing splint inside test tube
• what is the test for chlorine?

  white litmus paper inside a test tube containing chlorine gas
• what is the test for carbon dioxide?

  Lime water test
• what is chromatography?

  an analytical method used to separate the substances in a mixture
• what are the phases of chromatography?

  • stationary = where molecules cant move e.g. paper
  • mobile = where molecules can move e.g. solvent (water)
• what is the rf value?

  the ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent
• what is the the rf value equation?

  rf = distance travelled by substance / distance travelled by solvent
• what is an anion?

  an ion with a negative charge
• what is a cation?

  an ion with a positive charge
• what is the test for halides?

  add dilute nitric acid followed by silver nitrate solution
• what colour do chloride, bromide, and iodide turn in the halides test?

  • chloride = white precipitate
  • bromide = cream precipitate
  • iodide = yellow precipitate
• what is the test for sulfates?

  add dilute hydrochloric acid followed by barium chloride solution to mystery solution. if sulfate ions are present, a white precipitate will form
• what is the test for carbonates?

  1. add a couple of drops of dilute acid
  2. connect the test tube to a test tube of limewater
  3. carbonate ions react to form carbon dioxide, which will turn the limewater cloudy
• whats the test for metal cations?

  add a few drops of NaOH solution to mystery solution
• what colour precipitate do these form in the test for metal cations with NaOH?

  • calcium = white
  • copper (ll) = blue
  • iron (ll) = green
  • iron (lll) = brown
  • aluminium = white
  • magnesium = white
• what colour do these metal cations turn in flame tests?

  • lithium = crimson
  • sodium = yellow
  • potassium = lilac
  • calcium = orange - red
  • copper = green
• what is instrumental analysis?

  using machines to analyse unknown substances
• what is a disadvantage of flame tests?

  if the sample contains a mixture of metal ions, the flame colours of some ions may be hidden by the colour of others
• what are 3 advantages of instrumental analysis?

  • sensitive - can detect the tiniest amounts
  • fast - tests can be automated
  • accurate
• what is an example of instrumental analysis?

  flame emission spectroscopy
• how does flame emission spectroscopy work?

  1. sample is heated in a flame
  2. light analysed in a spectroscope
  3. a line spectrum of different wavelengths of light is produced
• what can line spectra be used in?

  • identify ions in solution - each ion has a unique line spectrum
  • determine the concentration of ions - calculated from the intensity of the lines