Chem 2

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Chem 2
2010-05-15 14:50:56
heat chemical rxn

Thermodynamics and Kinetics
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  1. used to develop criteria for predicting the direction of a chemical reaction
    is the reaction spontaneous? occuring on it's own without added work? and Time?
    Thermodynamics and Kinetics
  2. Study of heat and work
  3. energy that is transferred by system-surrounding until thermal equilibrium is established. (not state functions)
    heat (q)
  4. energy transfer between system and surrounding but results in (w=fxd) movement.
    (not state functions)
    Work (w)
  5. the universe
  6. specific part of the universe that is of interest
  7. 3 types of system
    open, closed and isolated
  8. matter and energy transfer can occur between system and surroundings
  9. only energy transfer can occur. Ex: earth
  10. no matter or energy transfer can occur ex. thermos bottle
  11. depends of the present state of the system not how it got there. (final + initial condition)
    state functions
  12. measures the energy absorbed or released as heat in a chemical or physical change
  13. absorbs energy
  14. releases energy, system releases energy to the surrounding
  15. measure of avg kinetic energy of the particles in a sample. higher the temp, molecules move faster
    KE = 1/2 mv^2
  16. amount of heat reqd to change temp. (intensive) always constant, the mass/ change in temp is a ratio.
    heat=mass x change in temp x specific heat capactiy
    (J) (g) (deg C) (J/g deg C)
    specific heat capactiy (cp)
  17. measure of systems capactiy to take up heat (extensive property)
    C=q/change in temp
    Heat capacity (C)
  18. Law of conversion of energy. energy cannot be created nor destroyed.
    qsyst + qsurr= 0
    qsyst = -qsurr
    First law of thermodynamics
  19. Energy = q+w
    q>0 toward the system (endo) heat absorbed w>0= work done on the system by the surr.
    q<0 away from the system (exo) heat released w<0= work done by the system on the surr
  20. H(heat of rxn)=u + pv
    -measured using a calorimeter
  21. energy available to do work
    gibbs free energy (delta G)
  22. delta H= Hfinal - H initial
    delta H>0 endothermic
    delta H<0 exothermic
    directly proportional to the amount of reactions/products involved
    enthalpy of reaction (delta H)
  23. allow chemists to find "H" (enthalpy) for reactions that cant be perfomed directly
    Hess's Law
  24. in any spontaneous process, the entropy (s) "disorder" of the universe is increasing. and remains unchanged in an equilibrium process.
    1. s<l<g
    2. increase in s, increase in T, particles moving faster
    3. delta S = Sprod - Sreact
    2nd law of thermodynamics
  25. products are favored
    free energy
  26. delta H<0, delta S>0
    Spontaneous free energy
  27. delta G
    if (-) spontaneous
    if (+) non spontaneous
    if (=0) equal
    delta G=delta H-TdeltaS
    (for S to be negative, temp needs to be low)
    Gibbs free energy
  28. delta H <0, delta H>0
    delta S <0, delta S>0 all depends on temperature
  29. Factors that can change a non spontaneous rxn to spontaneous rxn:
    • Temp
    • couple a ns rxn with one that is spont
    • pressure
  30. every substance has a finite(f) entropy, but at zero Kelvin, the entropy may become zero as in the case of a perfect crystal
    3rd law of thermodynamics
  31. speed of any change over a period of time
    amount of mol (react)/ time
  32. atoms, ions and molecules react to form products when they collide provided particles have enough kinetic energy.
    collision theory
  33. factors affecting reaction rates
    • Temp-energy move faster
    • catalyst
    • concentration-the more qty the more reaction
    • particle size-the more you have---> rxn faster
  34. if stress is applied to a system in dynamic equlibrium, the system changes to relieve the stress
    Le Chateliers principle
  35. 3 types of stresses
    • change in R/P
    • change in temp
    • change in P/ change in V (gases)

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