Chem 2

• When the collective internal energies of the reactants in a chemical reaction are different from those of the products—and they nearly always are—the difference constitutes the change in energy (ΔE) that accompanies the reaction.
• Enthalpies of formation are used to calculate the enthalpy changes associated with any chemical reaction by using Hess’ law
• The enthalpy change, or heat of reaction, is defined as the amount of energy transferred to or from a system at constant pressure during a chemical reaction
• change in energy is easier to measure than a system's internal energy because it is proportional to the to the system state or temperature.
• First law of thermodynamics: The total energy of the universe is a constant.
• Second Law of Thermodynamics states that the total entropy of an isolated system will never decrease over time
• ΔEuniv =0

  the energy of the universe cannot be destroyed because f the first law of thermodynamics.

  A) energy of system

  
• unit for internal energy: J/K mol-1
• Specific internal energy is the energy stored in the particles of a substance.

  commonly symbolized by the lowercase letter u
• Equation of change in internal energy: ΔU = ΔH + ΔS
• equation of change of Internal Energy of a Closed System: ΔH = ΔQ + ΔW
• What does u, q and W mean in the equation of change of internal energy of closed system?

  u represents the change in internal energy, q represents the heat added to the system, and W represents the work done on or by the system.
• what does q>0 mean when talking about internal energy?

  Heat is in
• what does q<0 mean when talking about internal energy?

  Heat is exiting out of the system.
• When does w become negative when discussing about internal energy?


  When the system does work on its surroundings.
• When does w become positive when discussing about internal energy?

  When work is done on the system
• intrinsic  energy means that every substance has a definite value of internal energy
• How do you not determine the final internal energy?

  Not considering the heat transfer and work done on or by the system.
• How do you determine the final internal energy?

  It depends on how much potential and Kinetic energy are available
• ΔE = Efinal − Einitial is the equation used to determine change of energy
• ΔE = q + w
• Entropy (S) is defined as the measure of disorderliness of a system. The greater the disorderliness, the higher the entropy. Entropy increases with temperature.
• the average kinetic energy of the molecules in a gas is directly proportional to its absolute (kelvin) temperature
• What happens when gases collide with one another ?

  They can undergo diffusion, react chemically, or bounce off each other.
• What are the types of molecular motion that contribute to the internal energy of a system? Vibrations, Rotations, and Translations