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Rates of Reaction (Graphs (product produced or reactant used over time,…

- - - - visual change
      - transparent to cloudy
      - how fast mark disappears
      - subjective and can't plot graph
      - E.g Sodium Thiosulfate + HCl
        
        both clear, react to form yellow precipitate of sulphur
        
        1 start with dilute Sodium Thiosulfate
        
        Place flask on paper with a black cross
        
        Add dilute HCl and start stop watch
        
        Record time when cross disappears
        
        Can change concentration and measure,
        time should be quicker
    - - most accurate as mass balance very accurate
      - as gas released mass disappears
      - can plot graph, measure at regular intervals
      - Disadvantage, releases gas straight into the room
    - - uses gas syringe to measure to nearest cm3
      - can measure at intervals
      - E.g Mg and HCl to produce H2
        
        add dilute HCl into conical flask
        
        Add Mg ribbon and quickly attach empty gas syringe
        
        Stop watch readings at regular interval, plot graph
        
        can change concentration or Mg amount but amount
        of acid should remain same to make sure it is a fair test
- - - - collision frequency - more collisions faster the reaction
      - energy transferred during collision (activation energy)
  - - - particles move faster
        
        more collisions
        
        more energy to make reaction happen
    - - more particles knocking about in same volume
        
        collisions more frequent
    - - If reactant is solid, breaking up,
        increases surface to volume ratio
      - will be more collisions more frequently
    - - speeds up without being use, not part of equation
      - decrease activation energy by providing
        alternative pathway with lower activation energy
      - Enzmes are biological catalysts