paper 2 chemistry

• increasing the temperature, pressure or concentration speeds up the rate of reaction
• the presence of a catalyst speeds up the rate of reaction
• the more collisions between particles, the faster the rate of reaction
• catalysts decrease the activation energy to speed up reactions
• rate of reaction = $\frac{amount\ of\ reac\tan t\ used\ or\ amount\ of\ produce\ formed}{time}$
• reversible reactions will reach equilibrium
• in reversible reactions, the temperature, pressure and concentration affect the position of equilibrium
• le chatelier's principle is the idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract this change
• hydrocarbons contain only hydrogen and carbon atoms
• alkanes have all c-c single bonds
• alkanes are saturated compounds in a homologous series. the first four are methane, ethane, propane and butane
• complete combustion: hydrogen+oxygen->carbon dioxide+water
• cracking requires a high temperature and presence of a catalyst
• cracking is used to break up large hydrocarbon molecules into smaller hydrocarbon molecules. there is greater demand for smaller hydrocarbon molecules because they are better fuels.
• chlorine bleaches damp litmus paper, turning it white
• if you put a glowing splint inside a test tube containing oxygen, it will relight
• bubbling carbon dioxide through an aqueous solution of limewater causes the solution to turn cloudy
• squeaky pop test: lit splint is held at the open end of a test tube containing hydrogen, it makes a squeaky pop sound
• to test for a carbonate, add dilute hydrochloric acid and bubble through limewater. if the limewater becomes cloudy, carbonates are present
• to test for sulfates, add dilute hydrochloric acid and barium chloride solution to the solution. a white precipitate of barium sulfate will form if sulfates are present
• to test for halides, add dilute nitric acid and silver nitrate solution.

  • chloride = white precipitate
  • bromide = cream precipitate
  • iodide = yellow precipitate
• flame tests to identify metal ions:

  • lithium = crimson flame
  • sodium = yellow flame
  • potassium = lilac flame
  • calcium = orange-red flame
  • copper = green flame
• when testing for sulfate ions, we have to add hydrochloric acid first to react with any carbonate ion impurities
• metal hydroxide tests:

  • calcium = white precipitate
  • copper = blue precipitate
  • iron(II) = green precipitate
  • iron(III) = brown precipitate
  • magnesium = white precipitate
  • aluminium = white at first, if in excess it redissolves to form a colourless solution
• pure water has a pH of 7 and contains no dissolved solids
• feedstock - a raw material used to provide reactants for an industrial reaction
• a petrochemical is a substance made from crude oil via chemical reactions
• cracking is a thermal decomposition reaction
• addition polymerisation reactions require high pressure and the presence of a catalyst
• alkenes join together by addition polymerisation
• ethanoic acid + ethanol -> ethyl ethanoate
• condensation polymers are biodegradeable
• amino acids combining to form a polypeptide is a condensation reaction
• thermosoftening polymers are made from lots of polymer chains held together by weak intermolecular forces
• thermosetting polymers are made from lots of polymer chains held together by strong covalent bonds
• desalination - the extraction of potable water from sea water
• the haber process - the industrial production of ammonia by using nitrogen and hydrogen
• the haber process requires:

  • temperature of 450
  • pressure of 200
  • iron catalyst
• the haber process is a reversible reaction that is exothermic in the forward reaction