Chemistry AS

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Chemistry AS
2012-01-17 15:18:04
chemistry alevel energy

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  1. Exothermic reactions
    • enthalpy change is negative
    • heat is given out
    • making of chemical bonds
    • Examples: combustion of fuels (CH4 + 2O2 -> CO2 + 2H2O), respiration (C6H12O6 + 6O2 -> 6CO2 + 6H2O)
  2. Endothermic reactions
    • enthalpy change is positive
    • heat is taken in
    • breaking chemical bonds
    • Examples: photosynthesis (6CO2 + 6H20 -> C6H12O6 + 6O2), thermal decomposition (CaCO3 -> CaO + CO2)
  3. Activation energy
    the energy required to start a reaction by breaking bonds
  4. Standard conditions
    • Pressure: 100 kPa / 1 atm
    • Temperature: 298K / 25oC
  5. Enthalpy change of reaction
  6. Enthalpy change of formation
    the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
  7. Enthalpy change of combustion
    the enthalpy change when one mole of a substance undergoes complete combustion under standard conditions. All reactants and products are in their standard states
  8. Enthalpy changes
    • energy change = mcT
    • enthalpy change = -energy change/moles
  9. Bond enthalpies
    energy required to break one mole of gaseous bonds to form gaseous atoms
  10. Hess' law
    • the enthalpy change is independent of the path taken
  11. Collision theory
    • rate increase: more frequent collisions, more successful collisions (increase surface area, increase pressure, increase concentration, increase temperature, use a light source, add a catalyst)
    • concentration on rate: increasing concentration increases collisions
    • pressure on rate: increasing pressure, particles get closer together, increases frequency of collisions
    • temperature on rate: increases temperature, particles get more energy, particle speeds increase
  12. Catalysts
  13. Boltzmann distribution
  14. Dynamic equilibrium
  15. le Chatelier's principle
  16. Chemical industry: compromise