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3.1: Free Energy

Terms in this set (19)

Free energy change
(deltaG) This can tell us whether a process will require energy or release energy (and then how much energy it will make available to do useful work)
Is the extraction of energy from adenosine triphosphate (ATP) favorable or unfavorable?
favorable free energy change
What is a system?
Any part of the universe that we choose for study. It must have defined boundaries.
What are the surroundings?
Anything that is not considered part of the system.
What is an isolated system?
A system that is unable to exchange energy and matter with its surroundings.
What is an open system?
A system that is able to exchange both energy and matter with its surroundings.
What is the first law of thermodynamics?
It states that in a closed system, energy is conserved. Energy can be neither created nor destroyed.
What is enthalpy?
(deltaH) The heat evolved in a reaction at constant pressure is equal to the change in enthalpy (deltaH).
- deltaH
The negative sign indicates that the reaction releases energy. The energy within the system decreased as this energy was transferred as heat to the surroundings.
What is a state function?
It depends only on the initial and final states of the system it describes, and is therefore independent of the pathway taken to get from the initial to the final state.
What are some examples of state functions?
Temperature, pressure, free energy, enthalpy, and entropy
Why can deltaH be measured in a calorimeter?
Because it is a state function that is only dependent on the final and initial conditions.
What are the two defining features of the equilibrium state for a system undergoing a reaction?
(1) it is the lowest energy state for the system
(2) the forward and reverse rates for the process are equal
What is an irreversible process?
It happens when systems are set up far from an equilibrium state. They then drive toward a state of equilibrium. (Spontaneous or favorable)
What is entropy?
(S) systems of molecules have a tendency to become less ordered. A degree of randomness or disorder in the arrangement of a system, measured by a state function.
What is the equation for entropy?
S = kb ln(W)

kb = the gas constant (R) / Avogadro's number
W = the number of substates of equal energy
What is the Boltzmann constant?
It is used in entropy and is defined as:
kb = the gas constant (R) / Avogadro's number
The entropy of a ordered state?
It is lower than that of a disordered state of the same system.
What is the second law of thermodynamics?
The entropy of an isolated system will tend to increase to a maximum value. Things will never become more ordered.
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