Ch. 19: Chemical Thermodynamics Flashcards
What is a spontaneous process?
happens on its own without any outside assistance
Are spontaneous processes reversible or irreversible?
ALWAYS irreversible
What is a nonspontaneous process?
the reverse of any spontaneous process | needs outside assistance
What is the direction of any spontaneous changes in chemical systems determined by?
loss of energy
Are all chemical and physical changes endothermic or exothermic?
EXOthermic
What is a reversible process?
can restore a system back to its original state with no changes to its surroundings
What is an irreversible process?
one that leaves the surroundings somehow changed when the system is restored to its original state
What type of process are REAL processes?
spontaneous processes = IRREVERSIBLE processes
What is entropy?
degree of disorder or randomness
What does entropy measure?
the tendency for the energy to spread = reducing its ability to accomplish work
What is the Second Law of Thermodynamics?
entropy of a universe increases for any spontaneous process
What does the “universe” consist of?
surroundings + system
What are microstates?
specific microscopic arrangements of atoms/molecules of a thermodynamic state
What does “W” represent?
number of microstates
What is Boltzmann’s constant?
1.38e-23 J/k
What trends must W temperature, volume, and number of molecules follow in order to increase entropy (S)?
W, T, V and number of molecules must increase
What are the 3 complex motions can every real molecule undergo?
translational | vibrational | rotational
What is translational motion?
movement in one direction
What is vibrational motion?
the periodic moving away/toward between atoms in a molecule
What is rotational motion?
molecule spins about an axis
What decreases entropy in chemical bonding?
formation of new bonds
What is the order of entropy between states of matter?
g > l > s
What are the 3 processes in which entropy increases?
solids/liquids —-> gases | solids —-> liquids | # gas molecules increases during rxn
What is the Third Law of Thermodynamics?
entropy of a pure crystalline substance at temperature absolute 0 is 0
What is the relationship between standard molar entropy (Sº) and molecular weight?
Sº increases as MW increases
What is Gibbs free energy?
the energy associated with a chemical reaction used to do work
What ∆G is associated with any spontaneous reaction? In which way does the reaction go?
∆G < 0 = -∆G | forward direction rxn
What ∆G is associated with any NONspontaneous reaction? In which way does the reaction go?
∆G > 0 = +∆G | reverse direction rxn
What does ∆G = 0 indicate about a reaction?
it is at equilibrium
At all temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , +∆H , -∆S ?
nonspontaneous
At all temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , -∆H , +∆S ?
spontaneous
At low temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , +∆H , +∆S ?
nonspontaneous
At low temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , -∆H , -∆S ?
spontaneous
At high temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , +∆H , +∆S ?
spontaneous
At high temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , -∆H , -∆S ?
nonspontaneous
