Chemical analysis

• cations


  positive ions
• anions


  negative ions
• potassium flame test


  lilac
• sodium flame test


  yellow
• Crimson red flame test

  Lithium
• calcium flame test


  orange-red
• Copper flame test


  green
• what type of ion (+/-) do flame tests check for?

  positive cations
• pure substance


  A single element or compound, not mixed with any other substance
• formulation


  a mixture of compounds, measured in quantities, that has been designed as a useful product
• why does chromatography work

  different compounds have different affinities for the solvent/paper stronger attraction for the paper = moves slower with the solvent.
• stationary phase in chromatography


  The paper because it does not move
• the mobile phase in chromatography


  The solvent that moves through the paper carrying different substances with it
• Rf value


  Distance travelled by substance / distance travelled by solvent
• lower Rf value


  higher affinity for the sovent than the paper
• lower rf value


  higher affinity for the paper than the solvent
• hydrogen test


  lit splint squeaky pop
• oxygen test


  Relights a glowing splint
• carbon dioxide test


  when bubbled through limewater, turns it cloudy
• chlorine test


  bleaches damp litmus paper
• Copper + sodium hydroxide


  Blue precipitate

  
• iron(II) + sodium hydroxide


  Green precipitate

  
• iron(iii) + sodium hydroxide


  brown precipitate
• aluminium + sodium hydroxide


  White precipitate
• aluminium + EXCESS sodium hydroxide


  dissolves, going colourless
• copper + sodium hydroxide equation

  cu2+ + 2OH- => cu(OH)2
• iron(II) + sodium hydroxide equation

  Fe2+ + 2OH- => Fe(OH)2
• iron(iii) + sodium hydroxide equation

  Fe3+ + 3OH- => Fe(OH)3
• calcium and sodium hydroxide equation

  ca2+ + 2OH- => Ca(OH)2
• magnesium + sodium hydroxide

  Mg2+ + 2OH- => Mg(OH)2
• aluminium + sodium hydroxide

  Al3+ +3oh- => Al(OH)3
• what type of ion (+/-) is adding sodium hydroxide testing for?

  cations
• testing for carbonate anions

  add dilute HCL. fizzing observed as CO2 released.
• sodium carbonate + HCL equation

  Na2CO3 +2HCL => 2NaCl + H2o + CO2
• testing for sulfate anions

  add a solution containing Ba2+ cations (BaCl2). white precipitate forms
• potassium sulfate + Barium chloride equation

  K2SO4 +BaCl2 => 2KCl + BaSO4
• testing for halide anions

  add dilute nitric acid, then add silver nitrate
• why is nitric acid added when testing for halide ions


  to remove any carbonate ions which would produce a white precipitate (silver carbonate)
• chloride + silver nitrate (colour)


  white precipitate
• bromide + silver nitrate (colour)


  cream precipitate