1. Equilibrium and Kinetics

2. Mechanical Equilibrium
Rectangular Block
Mechanical Equilibrium
Centre Of
Gravity

3. Pot. Energy Height of CG Configuration Unstable Metastable state

4. Global minimum = STABLE STATE Local minimum = METASTABLE STATE
Kind of equilibrium can be understood by making small perturbations
Global minimum = STABLE STATE
Local minimum = METASTABLE STATE
Maximum = UNSTABLE STATE

5. Intensive Properties Extensive Properties
Independent of the size of the system
e.g. P, T
Extensive Properties
Dependent on the quantity of material
e.g. V, E, H, S, G

6. Internal Energy = E = KE + PE
Some thermodynamic terms
Interactions in the solid (bonds)
Internal Energy = E = KE + PE
Vibration / Translation / Rotation

7. Enthalpy = H = E + PV Measure of the heat content of the system
At constant pressure the heat absorbed or evolved is given by H
Transformation / reaction will lead to change of enthalpy of system
Enthalpy = H = E + PV
Work done by the system
For condensed phases PV << E  H ~ E
H0 represents energy released when atoms are brought together from the gaseous state to form a solid at zero Kelvin
Gaseous state is considered as the reference state with no interactions

8. Gibbs Free Energy = G = H  TS
For a transformation that occurs at constant temperature and pressure the relative stability of the system is determined by its
GIBBS FREE ENERGY
Absolute Temperature
Gibbs Free Energy = G = H  TS
Entropy
Entropy is a measure of the randomness of a solid
G =  H  T  S
Even endothermic reactions are allowed if offset by TS

9. No. of different configurations of equal PE
Entropy
Microscopic
Macroscopic
Thermal
Configurational + other
H,E –ve at zero K But thermal S is zero
Sthermal increases on melting at constant temperature
Zero or +ve
Boltzmann constant
No. of different configurations of equal PE
Actually these are two interpretations of Entropy

10. Configurational Entropy change due to mixing A and B (pure elements)
S = Smixed state  Spure elements (A & B)
Zero
Stirling’s approximation
Ln(r!)=r ln(r)  r

11. Possible configurations of in an 1D system of 4 sites and two different species
Due to the statistical nature of the configurational entropy the equation is valid for a large number of species

12. Helmholtz Free Energy = A = E  TS
For a transformation that occurs at constant temperature and volume the relative stability of the system is determined by its
HELMHOLTZ FREE ENERGY
Helmholtz Free Energy = A = E  TS

13. KINETICS

14. Arrhenius equation Order wrt A Rate Constant Concentrations
Activation Energy Affected by catalyst
Arrhenius equation
T in Kelvin
Frequency factor
A is a term which includes factors like the frequency of collisions and their orientation. It varies slightly with temperature, although not much. It is often taken as constant across small temperature ranges.

15. Fraction of species having energy higher than Q (statistical result)
ln (Rate) →
0 K

16. Reactants Products A + BC AB + C A + BC (ABC)* AB + C
Activated complex

17. (ABC)* ΔH Energy A + BC AB + C Configuration Activated complex
Preferable to use G ΔH
Energy
A + BC
AB + C
Configuration

18. The average thermal energy is insufficient to surmount the
The average thermal energy is insufficient to surmount the activation barrier (~ 1eV)
The average thermal energy of any mode reaches 1eV at ~ K
But reactions occur at much lower temperatures
Fraction of species with energies above the activation barrier make it possible
Lost species by reaction are made up by making up the distribution
Rate  fraction of species with sufficient energy Rate  vibrational frequency (determines the final step)
Rate  n