Statistical thermodynamics Flashcards
What is the Gibbs free energy equation?
G = H - TS
Write an equation linking the enthalpy of a system with internal energy and the state variables pressure and volume
H = U + pV
What does Stirling’s approximation state?
For very large N: lnN! ~ NlnN - N
What does the distribution of molecules in a system depend on?
Temperature (gives energy to the system.
What does the Boltzmann distribution tell us?
Tells us that the population of the ground state in a system is determined by:
- the number of particles in a system
- how accessible the higher states are at the temperature of the system
What is q and what does it tell us?
q= total partition function; tells us how easy it is for a particle to escape from the ground state to higher levels, ie how many energy levels we might hope to fill.
What terms can the partition function be split into?
Nuclear- vibrational, rotational, translational
Electronic
What do the quantum mechanical energy levels for a rotating molecule depend on?
Its shape because of the different moments of inertia.
How many moments of inertia does a diatomic/linear molecule have?
1
How many moments of inertia does a symmetric top have?
2
How many moments of inertia does an asymmetric top have?
3
What is the symmetry number for heteronuclear and homonuclear diatomic molecules?
Heteronuclear= 1 Homonuclear= 2
How can the symmetry number be worked out for polyatomic molecules?
Look at the point group for the molecule and sum the total number of pure rotational operations and the identity operator.
How many vibrational normal modes are there for linear and polyatomic molecules?
Linear: 3N - 5
Polyatomic: 3N - 6
