Thermochemistry

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Author:
Bwatkins
ID:
76852
Filename:
Thermochemistry
Updated:
2011-04-02 23:25:40
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Chemistry Thermodynamics
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Description:
Terms associated with thermodynamic aspects of chemistry.
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  1. Define Thermodynamics
    The study of energy and its transformations.
  2. Define Thermochemistry
    The transformations of energy, particularly heat, in chemical reactions.
  3. What is the formula for kinetic energy?
    • EK = (1/2)mv2
    • m = mass
    • v = velocity
  4. What is the SI unit for energy?
    Joule = 0.23885cal = 6.2145 * 1018eV
  5. What is the SI unit of power?
    Watt = J/sec
  6. What is the equation for potential energy?
    • EP = mgh
    • m = mass
    • g = acceleration constant of gravity (6.67259 * 10-11(m3/kg*sec2)
    • h = height (relative to the surface in the earth)
  7. Define System
    The substance under study in which a change occurs.
  8. Define Surroundings
    Everything in the vicinity of the system.
  9. Define Internal Energy (U)
    The sum of the kinteic energy, potential energy, and the energy inherent to the particles.
  10. What is the equation for total energy?
    Etot = EK + EP + U
  11. Define Heat (q)
    The energy that flows in or out of a system because of a temperature difference between the system and its surroundings.
  12. Define Endothermic
    The system absorbs energy (+q)
  13. Define Exothermic
    The system evolves energy (-q)
  14. Define Heat of Reaction
    • The value of q required to return a system to the given temperature at the completion of a reaction.
    • qp = heat of reaction at a constant pressure (typically assume atomospheric)
  15. Define Enthalpy (H)
    An extensive property of a substance that can be used to obtain the change in q in a reaction. Enthalpy is a state function, i.e. it is a property of a system that depends only on its present state.
  16. What is the relationship between enthalpy of reaction and heat of reaction?
    • Change in H = qP
    • Change in H = Hproducts - Hreactants
  17. What equation relates U to H?
    • Change in U = Change in H - P * (change in V)
    • P = pressure
    • V = volume
  18. What is the change in energy (E) of a system?
    • Change in E = q + w
    • q = heat
    • w = work
  19. What is the first law of thermodynamics?
    The change in internal energy (U) of a system is the sum of the heat and work.
  20. Define Work
    • The energy exchange that results when a force (F) moves and object through a distance (d).
    • w = F * d
  21. Define Calorimetry
    A measure of the heat transfered between a system and its surroundings.
  22. Heat Capacity
    The amount of heat required to raise the temperature of a sample by 1K.
  23. Define Specific Heat Capacity
    • The amount of heat required to raise 1 gram of a substance 1K.
    • Molar = the amount of heat required to raise the temperature of 1 mole of a substance 1K.
  24. Diagram a Bomb Calorimiter
  25. Define Hess's Law
    In a reaction carried out in a series of steps the change in enthalpy for the reaction will equal the sum of the enthalpy changes for the individual steps.

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