A2 Revision Notes

My name is Sophie. I am currently in year 13 studying maths, chemistry and biology. i thought starting a blog to store my revision notes would be a cool idea. feel free to have a look, ask questions, correct me, whatever.

Anonymous asked: C3, MEI? Possibly? Thanks in advance!

Any specifics? Differentiation? Integration? Logs?

Nitration of Benzene

Conditions - Benzene is treated with a mixture of concentrated Nitric acid and concentrated Sulphuric acid (H2SO4 being the catalyst as it is regenerated at the end of the reaction)

Reaction to produce the reactive intermediate-

Mechanism:

Eutrophication

Eutrophication can be caused by leeching or sewage pollution 

Leeching - Water soluble molecules are washed out of the soil by rain into nearby rivers and ponds. 

  • Excess nitrates=stimulated algae growth 
  • Lots of algae leads to sunlight becoming blocked from the plants growing below
  • Plants dies because the cannot photosynthesize enough
  • Bacteria feed on dead plant matter
  • More bacteria=more respiration=lower oxygen concentration in the water
  • Fish and other organisms die due to not enough oxygen being available for respiration

The Nitrogen Cycle

Plants absorb nitrates

  • transported up the xylem from the roots (taken in by active transport)
  • they are used to synthesise proteins

-Animals get nitrogen from plants by consuming them

-The excrete excess amino acids as urea or ammonia into the soil.   

AMMONIFICATION

  • Nitrogen compound in the soil fro dead animals, plants and waste products
  • They are broken down by SAPROPHYTES into ammonia. They use saprophytic digestion by secreting enzymes 

NITRIFICATION

  • Ammonium converted into nitrates by nitrifying bacteria in a series of oxidative reactions

DENITRIFICATION

  • Done by denitrifying bacteria. 
  • This occurs on anaerobic conditions where there is very little to no oxygen available eg. bogs, waterlogged soils 
  • Nitrogen is released as a gas to the atmosphere 

NITROGEN FIXATION

  • This is done my nitrogen fixing bacteria eg. Rhizobium
  • Nitrogen gas is fixed into a form which plants can use such as ammonium (used to synthesise amino acids)
  • Bacteria exist in small nodules of LEGUMINOUS plants (clovers, peas) or can be free living in the soil
  • They use the enzyme nitrogenase to fix nitrogen gas at low temperatures. 
  • Bacteria in the nodules have a mutualistic relationship with the plants - the bacteria get sugars from the plant while the plant gets nitrates from nitrogen fixation