Lec4-6 Thermodynamics

• What is the main focus of thermodynamics?

  Direction a reaction is favored to go
• What does kinetics study?

  Rate of reactions
• What is a system in thermodynamics?

  Part of the universe that is of interest
• What are the types of thermodynamic systems?

  • Isolated: no exchange of matter or energy
  • Closed: exchange energy, not matter
  • Open: exchange energy and matter
• What type of system are living organisms?

  Open
• What is heat (Q) in thermodynamics?

  Energy transfer by random motion
• How is work defined in thermodynamics?

  Energy transfer by organized motion
• What does the First Law of thermodynamics state?

  Energy cannot be created or destroyed
• How is the energy change of a reaction determined?

  By initial and final states of the system
• Why must energy change of a reaction be independent of the pathway taken?

  To prevent energy generation through cycling
• Why is energy considered a state function?

  Depends only on the current state of a system
• What is enthalpy (H) of a reaction?

  Heat change at constant pressure
• What does the equation for ΔH represent?

  ΔH = ΔU + PΔV
• What does ΔU represent in the equation for ΔH?

  Internal energy
• What does P represent in the equation for ΔH?

  Pressure
• What does ΔV represent in the equation for ΔH?

  Change in volume
• What is the Second Law of thermodynamics?

  Spontaneous reactions increase entropy of the universe
• What is entropy?

  Measure of disorder/randomness of a system
• How is entropy related to molecular configurations?

  Related to number of equivalent arrangements
• What is Gibbs Free Energy (G)?

  Free energy available for a system to do work
• What are the units for enthalpy, free energy, and entropy?

  J/mol or KJ/mol
• What is the value of G when a reaction is at equilibrium?

  0
• Why is G equal to 0 at equilibrium?

  Small changes allow reaction in either direction
• Why is free energy change considered extensive?

  Depends on the amount of material present
• What does the sign of change in G indicate?

  Negative: spontaneous forward, positive: reverse
• Which factors affect the free energy change of a reaction?

  Altering concentrations and coupling reactions
• What are the key equations linking free energy change to concentration?

  1. ΔG = ΔG° + RT ln(Q)
  2. ΔG° = -RT ln(Keq)
• What are standard conditions in thermodynamics?

  1 atm pressure, 25°C temperature
• What is the relationship between the equilibrium constant and free energy change?

  ΔG° = -RT ln(Keq)
• How do you find Keq of a multi-step reaction?

  Multiply equilibrium constants of each step
• What happens to Keq for reverse reactions?

  Keq becomes a reciprocal
• What happens to Keq if reaction coefficients are multiplied by n?

  Keq is raised to the power of n
• What does it mean to couple reactions?

  Endergonic reactions paired with exergonic reactions
• Why is ATP considered the main energy currency of the cell?

  Relatively negative free energy change in hydrolysis
• What stabilizes the inorganic phosphate during ATP hydrolysis?

  Resonant hybrid stabilization
• Why is ATP hydrolysis kinetically stable?

  High activation energy prevents rapid reaction
• How does ATP hydrolysis allow energy regulation in cells?

  Specific enzymes regulate energy distribution