exmqa vidoeo

• | equilibrium

  1. speed of forward & backward reactions are the same
  2. happens in a closed system
  3. overall concentration stays same
• | le chatelier's principle

  • position of equilbrium will shift to counteract change by change in..
  • temperature
  • pressure
  • concentration
• • forward reaction is exothermic
• • backward reaction is endothermic (+)
• • if temperature is increased the equilibrium will shift to the left to decrease temperature
  • ratio of reactants increases
• • when PRESSURE increases, equilibrium will shift to where there are less molecules
  • more products
• • if you increase CONCENTRATION of products, reactants will increase
• catalysts do NOT effect position of equilibrium
• catalyst speeds both reactions equally
• | measuring rates

  1. mix sodium thiosulfate & HCl into flask over a cross
  2. start stopwatch & keep eye on cross as precipitate forms
  3. stop stopwatch & record time for cross to disappear
  4. repeat with different concentrations of HCl
  5. plot graph of time taken vs concetration
  6. higher concentrations = less time
• activation energy: minimum energy needed to start a chemical reaction
• reaction will only occur if particles have enough energy to react; energy of particles have to be greater than activation energy
• rate of reactions: frequency of collisions
• 5 factors that affect rate

  • temperature: more kinetic, more collisions
  • pressure: particles closer
  • surface area: more surface area, more surface to collide
  • concentration: more particle in same volume
  • catalyst: reduces activation energy, more particles can react
• | air pollution

  • carbon dioxide
  • made during complete combustion
  • not toxic but causes global warming
• • carbon monoxide
  • incomplete combustion
  • binds to RBC so we can't carry oxygen
• • soot
  • incomplete combustion
  • absorbs sunlight
  • breathing problems
• • sulfur dioxide
  • burning fossil fuels due to sulfur impurities
  • makes acidic rain & affects trees, lakes & limestone buildings
  • respiratory problems
• • nitrogen oxides
  • energy from lightning or heat of burning
• • potable water: not contain many dissolved substances
• potable water comes from...

  fresh water

  sea water

  reverse osmosis
• • fresh water is collected from ground or surface
  • filtrate to remove large undissolved substances
  • sterilisation with chlorine or UV to kill microbes
• • sea water is tooooo salty
  • use distillation
  • add water & seal with bung
  • heat solution so vapour evaporates
  • vapour cools & condenses
  • collect liquid in beaker
  • too expensive
• • reverse osmosis
  • low to high through partially permeable membrane with energy
• | waste water treatment

  1. filtered to remove large objects
  2. remaining waste goes into container until it forms 2 layers- sedimentation- bottom layer is sludge, top layer is effluent
  3. sludge goes to anaerobic digester to be broken down into fertilliser
  4. effluent goes to aerobic digestion; adding oxygen removes bad microorganisms
  5. now it can return back into river
• • impurities
  • increases boiling point
  • increases range
  • decreases melting point j