C3303 Midterm 1 Flashcards
Classical thermodynamics
Relationship between mechanical and thermodynamic variables of a system
Mechanical Properties
Describe overall composition / position of a state; P, T, V
Thermodynamic Variables
Describe internal macroscopic state; U, H, A, G
Microcanonical Ensemble
Isolated system; no E and matter can exchange between the system and surroundings; V fixed
Canonical Ensemble
E can transfer across the boundary, but not matter; V is fixed
Isothermal-isobaric ensemble
Energy can transfer across boundary, but not matter; V of system can change such that the P is constant
Volume, units and in ensembles
m^3; in microcanonical and canonical, V is constant. A distribution of volumes is possible in isothermal-isobaric
Pressure of system, ensembles
in microcanonical and canonical, P depends on state of system; in isothermal-isobaric, the volume changes so the P of system is equal to P of surroundings
Internal energy
total E needed to create the system
What type of E describes intermolecular interactions?
U-pot
Enthalpy
Total E of system and E required to create a volume, V
Heat
thermal E transferred from surroundings to system
Work
E corresponding to expansion of system against surroundings
First Law of Thermo
dU=dq+dw
Entropy
Complexity; dS=dqrev/T
How is spontaneity determined
By change in E and entropy; Gibbs Energy and Hemholtz Energy
A equation
A=U-TS
G equation
G=H-TS
Pressure, T, heat capacity differential relations
p=-dU/dV
T=dU/dS
Cv=dU/dT
What are the limitations of classical thermodynamics?
No direct relationship between chemical structure and thermo; doesn’t allow us to predict dG of a reaction, but does explain why dG must be negative for spontaneity
Approximations to simplify models, ideal gases
Ideal gases have no intermolecular interactions and gas particles have no volume (point masses); ideal gases only have kinetic E
Equipartition Theorem
U=1/2*nDOFnRT
Degrees of Freedom
Number of independent ways the particle can move, resulting in a change to the original position. Depends on composition of gas particles
What are the 3 types of DOF?
- Translations: entire molecule in a direction
- Rotations: spinning along an axis
- Vibrations: stretching/bending of bonds
Can connect to other thermo parameters