Chapter 19 - Chemical Thermodynamics Flashcards
What is “chemical thermodynamics”? (Brief categorization)
The area of chemistry that deals with energy relationships.
What is the first law of thermodynamics?
Energy is conserved (neither created nor destroyed).
How is enthalpy mathematically expressed?
ΔE = q + w
ΔE is the change in the internal energy of a system
q is the heat absorbed or released by the system
w is the work done by or on the system
What does q > 0 mean?
What does w > 0 mean?
It means that the system is gaining heat from the surroundings.
It means that the system is gaining work from the surroundings.
What is a spontaneous process?
One that proceeds on its own without any outside assistance. It only goes in one direction.
What is a nonspontaneous process?
The reverse of a spontaneous process. It does not occur without outside assistance (or at all, really).
Thermodynamics tells us about the ____ and ____ of a reaction but not ____. What deals with the latter?
Thermodynamics tells us about the direction and extent of a reaction but nothing about the rate. Kinetics does that.
What is a state function?
Properties that define a state and do not depend upon how we reach that state. Examples: temperature, internal energy, and enthalpy.
What is a reversible process?
A specific way in which a system changes its state. We can restore the system back to its original state without a net change.
What is an irreversible process?
One that cannot be reversed to restore the system to its original state without a net change.
What is entropy?
The “randomness” of a system
What is the second law of thermodynamics?
The entropy (“randomness”) of the universe is always increasing.
What is a microstate?
A single possible arrangement of the positions and kinetic energies of the molecules when the molecules are in a specific thermodynamic state.
What is Boltzmann’s entropy formula?
S = k • ln(W)
k is the Boltzmann constant: 1.38 • 10-23 J/K
Regarding the Boltzmann formula, entropy is a measure of what?
Entropy is a measure of how many microstates are associated with a particular macroscopic state.
What is translational motion?
The movement from point A to point B, like throwing a baseball.
What is rotational motion?
Motion of molecules in which they spin around an axis.
What is vibrational motion?
Motion in which atoms periodically move towards and away from one another.
The number of microstates possible for a system increase when ____ and why?
The number of possible microstates increases with an increase in temperature, volume, or number of molecules because these changes increase the possible positions and kinetic energies of the molecules making up the system.
What is the third law of thermodynamics?
The entropy of a pure, perfect crystalline substance at absolute zero is zero: S(0K) = 0.
What is the formula for Gibbs free energy?
ΔGº = ΔH - TΔS
H is enthaply
T is temperature
S in entropy
Describe ΔG > 0, ΔG = 0, ΔG <0.
ΔG < 0 means the reaction is spontaneous in the forward direction.
ΔG = 0 means the reaction is at equilibrium
ΔG > 0 means the forward direction is nonspontaneous (work must be done to make it occur)
In any spontaneous process carried out at constant temperature and pressure, what happens?
The free energy always decreases.
