chem topic 9

• polymers

  substances of high average relative molecular mass made by joining monomers together
• monomers 


  small repeating units that makeup addition polymers and have a double covalent bond
• what is the test for cations

  flame test + metal hydroxides characteristics
• flame test

  1. dip the nichrome wire loop into the concentrated HCl + rinse it in distilled water to clean it
  2. dip the NWL into the metal compound and then put it into the hottest bit of the Bunsen burner
  3. Record what colour the flame goes based on the metal ion present
• what part of the Bunsen burner do we dip the nichrome wire loop into + why

  the middle clear blue bit - bc its the hottest part
• what colour does the flame go if Li+ is present

  RED
• what colour does the flame go if Ca2+ is present

  Orange
• what colour does the flame go if Na+ is present

  Yellow
• what colour does the flame go if Cu2+ is present

  Blue
• what colour does the flame go if K+ is present

  Lilac
• 3 characteristics in metal hydroxides

  • insoluble
  • form a precipitate in solution when formed
  • have characteristics colour
• to detect cations

  • add NaOH to the metal compound + if a hydroxide precipitate forms you can use its colour to find out what ion was in the compound
  • add more NaOH
  • if you get a white precipitate it means its either Al3+ or Ca2+. then you add more NaOH and then if its colourless = Al3+ bc its dissolves
  • if it stays white = Ca2+ bc it doesnt dissolve
• test for NH4+ ions

  1. add NaOH and gently heat it and ammonia gas will be given off
  2. then you can test for ammonia gas
• tests for ammonia gas

  1. damp red litmus paper turns blue
  2. ammonia has a strong smell - high concs of it = can be an irritant + toxic
• test for anions - halide

  1. add dilute nitric acid - to get rid of any carbonate ions that would confuse the results
  2. Add AgNO3- will react w/ the halide + form a coloured precipitate from which u can tell which halide it is
• what colour precipitate does Cl - form in the halide test for anions

  white
• what colour precipitate does Br - form in the halide test for anions 


  cream
• what colour precipitate does I - form in the halide test for anions 


  yellow
• test for anions - sulphate ions

  1. add dilute HCl - removes any carbonates to stop them from reacting
  2. add barium chloride solution - reacts w/ any SO42- ions + forms a white precipitate.- barium sulphate
• why do we add dilute HCl in the test for anions - sulphate ions test

  to remove any carbonates to stop them from reacting
• why do we add barium chloride solution in the test for anions - sulphate ions test

  it reacts with any SO42- ions + forms a white precipitate - BARIUM SULPHATE
• test for anions - carbonates

  1. add dilute HCl to the solution - if CO32- is present effervescence occurs + CO2 is given off
  2. CO2 goes thru the delivery tube and into the limewater
  3. turning it from colourless --> milky
• what is effervescence and what does it show

  it is fizzing + shows a gas being given off
• formula for the test for anions - carbonates test

  carbonate ion + HCl --> CO2 + H20
• Flame photometry

  Used in dilute ion solutions
• Flame photometry process

  1. Heat up the solution

  2. Ions get energised

  3. Electrons cool down to their original levels

  4. Transfer the energy as light

  5. Light passes through a spectroscope

  6. Produces a light spectrum based on each wavelength released
• Flame photometry

  • Can be used to identify ions in mixtures
  • Can be used to see the concentration of an ion there is in a solution
• Intensity of the wavelength

  • Shows the concentration of the ion
  • Can be worked out using a calibration curve
• Advantages of using machines such as Flame Photometry

  • Very fast
  • Accurate - no human error
  • Sensitive - detect tiniest amount of substances
• alkanes 


  saturated homologous series of hydrocarbons

  (saturated = full, cant fit any more = no double bonds)
• alkenes 


  unsaturated homologous series of hydrocarbons

  have 1 C=C functional grp
• general formula for alkane

  CnH2n+2
• general formula for alkene

  CnH2n
• test for alkEne 


  mix the alkene w/ bromine water + it will decolourise from orange to colourless bc an addition reaction takes place causing Br to be added across the double bond

  A) draw this

  
• alkenes name them + draw

  
• what is meant by unsaturated hydrocarbon

  a compound of hydrogen + carbon only

  contains double bonds between the carbon atoms
• why are alkanes saturated hydrocarbons 


  the hydrocarbon has only single bonds and that the hydrocarbon contains the maximum number of hydrogen atoms for each carbon atom
• what is a functional group of atoms 


  a group of atoms that determine how a molecule acts

  members of a homologous series all have the same functional grp
• why are alkenes unsaturated hydrocarbons

  bc they contain a C=C functional grp

  they can make more bon
• hydrocarbons are oxidized in combustion reactions