topic 9

• What colour flame is lithium?

  Crimson red
• What colour flame is sodium?

  yellow
• What colour flame is potassium?

  lilac
• What colour flame is calcium?

  orange-red
• What colour flame is copper?

  blue-green
• Describe the method for a flame test?

  1) clean a in chrome wire loop in HCl

  2) dip wire loop into metal

  3) hold loop in clear part of a blue bunsen flame
• How to test metals? (not flames)

  add some sodium hydroxide, as many metal hydroxides are insoluble and have distinct colours, so we can see the precipitate.
• What colour is the Al(OH)3 precipitate?

  White, but then re dissolves in excess NaOH to be colourless (this is Al(OH)4)
• What colour is the Ca(OH) precipitate?

  white
• What colour is the Cu(OH)2 precipitate?

  blue
• What colour is the Fe(OH)2 precipitate? (indicating Fe2+)

  Green
• What colour is the Fe(OH)3 precipitate? (indicating Fe3+)

  Brown
• How do you test for ammonium?

  Add NaOH to produce ammonia

  Test for ammonia using damp red litmus, which should turn blue
• How do you test for Halide ions?

  Add dilute nitric acid and then silver nitrate solution
• What halide ion tests do you need to know? (include colours of precipitate)

  chloride - white precipitate of silver chloride

  bromide - cream precipitate of solver bromide

  iodide - yellow precipitate of silver iodide
• How do you test for carbonates?

  Use dilute acid and add it to the test tube that contains your mystery substance. Connect this to a test tube containing lime water. If the limewater goes cloudy, carbonates are present. (the CO2 supposedly produced should travel through the tube to the limewater)
• What do you test for sulfate ions?

  Add HCL to prevent non-sulphate ions reacting

  Add barium chloride, a white precipitate of barium sulphate should form.
• What is flame photometry?

  an instrumental method that allows you to identify ions in a dilute solution by analysing the spectra of light frequencies of light emitted.
• What are the advantages of using a machine to analyse an unknown substance?

  - very sensitive (can even detect tiny amounts)

  - very fast and tests can be automated

  - very accurate as they remove human error
• What are alkanes?


  saturated hydrocarbons containing only single bonds
• What is the general formula of alkanes?

  2n+2
• What is the general formula of alkenes?

  2n
• What is the functional group of alkenes?

  C=C
• What are the uses of alkenes?

  To make plastics and alcohol
• What are the uses of alkanes?

  fuels
• What is the source of alkenes?

  cracking, dehydrating alcohols
• What is the source of alkanes?

  crude oil
• How do you test for alkanes/ alkenes?

  > bromine water is an orange liquid

  > Br water does NOT react with alkanes so it stays orange

  > it DOES react with alkenes - it decolourises water from orange to colourless
• In combustion reactions, what happens to hydrocarbons?

  they are oxidised
• What happens in an addition polymerisation reaction?

  Unsaturated monomer molecules join together to form saturated polymers. The double bond opens up, allow two new bonds (one on each end of the molecule) to form.
• What are the properties and uses of poly(ethene)?

  - flexible, electrical insulator, cheap

  - used in plastic bags, bottles, wire insulation
• What are the properties and uses of poly(propene)?


  - flexible, strong, tough, mouldable

  - crates, furniture, ropes
• What are the properties and uses of poly(chloroethene)? (PVC)

  - tough, cheap

  - window frames, water pipes
• What are the properties and uses of poly(tetrafluoroethene)? (PTFE)

  - unreactive, tough, non-stick

  - non-stick pans, waterproof clothing
• Name some examples of naturally occurring polymers?

  - DNA (nucleotide monomers)

  - protein (amino acid monomers)

  - carbs (sugar monomers)
• What are dicarboxylic acid monomers?

  They contain 2 carboxylic acid
• What are diol monomers?

  They contain 2 alcohol groups
• When do polyesters form?

  When dicarboxylic acid monomers and diol monomers react together in a condensation reaction
• What is the functional group of an ester?


  Ester link (-COO-)
• What is lost in a condensation reaction?

  water molecule