Chemical analysis

• purity 


  Contains only one type of compound or element e.g pure water or sodium chloride
• Pure + impure substance

  Pure = melt + boil and specific temp

  this helps us figure out what substances are

  impure = melt and boil over range depending on amounts of substances in it
• Formulation


  Mixture prepared using specific formula with precise amounts of components for a particular function e.g paint medicines and cleaning products
• Paper chromatography 


  Method:

  draw a line near bottom of filter paper in pencil (baseline)

  then add sample of inks on the line

  in beaker add small amount of solvent (water or ethanol)

  secure filter paper on splint w paper clip and lower into solvent

  solvent should be below baseline

  wait for solvent to seep up separating dyes

  take out and leave to dry
• Mobile phase 


  Substance the molecules can move in (solvent)
• Stationary phase 


  Substance the molecules can’t move in (paper)
• Chromatography results


  Substances more soluble spend more time in the mobile phase = move faster

  substances less soluble spend less time int the mobile phase = move slower
• Rf value


  distance travelled by substance divided by distance travelled by the solvent
• Tests for chlorine (poisonous) 


  Test tube of sample gas

  take damp blue litmus paper

  put it in tube

  if present it will turn white (may briefly turn red)

  do in fume cupboard
• Test for oxygen 


  Take a glowing splint

  get sample of gas and place splint in openning of tube

  splint should relight if oxygen present
• Test for hydrogen 


  Test tube of sample and burning splint

  place near test tube and should hear a squeaky pop if hydrogen present
• Test for carbon dioxide


  Get gas sample in one tube

  and lime water in another

  use a tube to connect the two

  if carbon dioxide present the line water should bubble and turn cloudy
• Tests for carbonate ions

  Carbonate + acid = salt + CO2 + water

  Add dilute HCl to sample

  collect gas

  add it to limewater in a test tube

  if cloudy = carbonate ions present
• Test for sulfate ions

  Add dilute HCl

  then add dilute barium chloride

  if a white precipitate forms = sulfate ions present
• Test for halide ions

  add dilute nitric acid to sample

  the add silver nitrate

  if white precipitate = chloride ions present

  if cream precipitate = bromide ions present

  if yellow precipitate = iodide ions present
• Flame test 


  Tests for positive metal ions

  dip sterile wire loop (or splint) into sample compound

  Hold over a roaring flame

  See what colour it burns to determine ions present
• Flame test results


  Lithium = crimson

  Sodium = yellow

  potassium = lilac

  Calcium = orange-red

  copper = green
• Metal hydroxide test


  Tests for positive metal ions

  React samples with sodium hydroxide solution

  the colour of the precipitate determines the ions
• Results of metal hydroxide test

  Copper III = blue precipitate

  Calcium = white precipitate

  iron II = green precipitate

  iron III = brown precipitate

  magnesium = white precipitate

  aluminium = white at first but if excess NaOH it becomes colourless
• Flame emission spectroscopy 


  For when samples contain multiple metals or metals of similar colours

  can detect the individual wavelengths that are emitted = each has its own unique line spectrum

  if lines are dull = low conc of ions

  if bright = high conc of ions
• Advantages of FES


  If a sample contains multiple metals the spectrum will show lines for all of them

  can the compare to specific metal ones to work out which are present
• Cons of FES


  expensive

  special equipment needed
• Manual vs instrumental tests

  Manual: basic and cheap

  instrumental: very accurate sensitive and fast, use expensive equipment