Lecture 1 Gibbs Energy Flashcards
define gibbs free energy
the maximum amount of non-expansive work done during a thermodynamic process
equation for gibbs free energy
G = H - TS
what values of gibbs free energy are non-spontaneous processes
larger than 0
what value of gibbs free energy are spontaneous processes
smaller than 0
what values of gibbs free energy are at equilibrium
0
process of molecular self-assembly in solid/vacuum interface
adsorption
diffusion
no desorption
process of molecular self-assembly at solid/liquid interface
adsorption
diffusion
desorption
is molecular self assembly at a solid vacuum interface spontaneous
yes it has delta G smaller than 0
delta H much smaller than 0
irreversible
how to find gibbs free energy with products and reactants free energy
products - reactants
what conditions is gibbs energy defined at
constant temperature and pressure
what do we get at conditions of constant temperature and volume
Helmholtz energy A
conditions for standard gibbs energy
pressure 1 bar
concentration 1 moldm^-3
how does temperature affect gibbs free energy
the higher the temperature the lower the free energy
gradient of -S
steep for gas less steep for solid and liquid
what does a stand for
thermodynamic activity
definition of thermodynamic activity
the effective concentration of the component
equation for thermodynamic activity of an ideal gas
a = p/p standard conditions
equation for thermodynamic activity for an ideal solution
a = [A]/[A] standard conditions
equation for thermodynamic activity of a pure liquid or solid
a (pure solid) = a (pure liquid) = 1
why define an equation using activity for gibbs free energy
can have dependence on pressure or concentration
equation for gibbs free energy referring to activity
G = Gstandard conditions + RT ln a
what conditions are ideal
dilute solutions
non-interacting gases at low temperatures
what is a in real systems
effective concentrations
equation for effective concentrations
aA = upsilonA [A]
when does upsilonA stand for
activity coefficient
what values can activity coefficient be
less than 1
other name for molar gibbs energy
chemical potential
equation for molar gibbs energy
mu i = (backwards deltaG/backwards delta ni)
ni = number of mols of compound
i and nj are the number of mols of other compounds
what is chemical potential independent of
number of mols of the system
