Collision theory

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Author:
Anonymous
ID:
102280
Filename:
Collision theory
Updated:
2011-09-17 11:53:16
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Collision theory chemistry
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Description:
Higher Chemsistry - Collision Theory
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  1. What is needed between particles before a reaction can take place?
    A collision
  2. Are all collisions between particles sucessful?
    No
  3. Why are not all collisions successful?
    As there is a minimum energy needed
  4. What is this minimum energy called?
    The activation energy. Symbol - EA
  5. Explain using collision theory how reaction rate increases if concenreation increases
    As concentration increases, the total number of collisions increases, causing more successful collisions, so the reaction rate increases
  6. Explain using collision theory how reaction rate increases if particle size decreases
    As the particle size gets smaller, then surface area gets bigger. This allows more total collisions to take place between reacting particles, making more sucessful collision and hence increasing the reaction rate
  7. Explain using collision theory how reaction rate increases if temperature increases
    • As the temperature increases, the particles move faster. This allows more total collisions to take place between reacting particles, making more successful collisions and hence increasing the reaction rate.
    • Also, because temperature is a measure of the average kinetic energy of the particles, when particles are heated the collisions between them are of higher energy. Therefore more of them are equal to or greater than the activation energy resulting in more successful collisions and making the reaction rate increase.
  8. A 10°C rise in temperature _______ the reaction rate?
    doubles
  9. What do catalysts do?
    They speed up a chemical reaction and are recovered chemically unchanged at the end of a reaction
  10. What are the two types of catalysts?
    • Heterogeneous - the catalyst is in a different state from the reactants
    • Homogeneous - the catalyst in in the same state as the reactants
  11. How do catalysts work?
    By lowering the activation energy for the reaction
  12. What is 'catalyst poisoning'?
    When impurities present in the reactants adsorb onto the surface of the catalyst taking up 'sites' which could otherwise have been occupied by reactant particles
  13. What are enzymes?
    Biological catalysts
  14. What kind of industrial process can enzymes be used in?
    Fermentation
  15. Why are catalytic converters fitted to car exhausts?
    To catalyse the conversion of poisonous carbon monoxide and oxides of nitrogen into carbon dioxide and nitrogen
  16. Name the metals that can be used a in catalytic converter
    • Platinum
    • Palladium
    • Rhodium
  17. Why do catalytic converters only use 'lead free' petrol?
    Since lead poisons the platinum metal which is used as the catalyst

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