Physical Transformation Flashcards
For a __ system to be at equilibrium, the chemical potential of each component should be ___ throughout the system, regardless of the ___ it is in.
multi-component; the same; phase
Chemical potential is an ___ property
intensive
If there is only __ component in a system, it can exist in ____ depending on the ___ and ___
single; different phases; pressure and temperature
At constant pressure: dGm/dT = ?
dGm/dT = -Sm
Arrange in increasing entropy (steepest slope dGm/dT):
solid liquid gas
solid liquid gas
gas has steepest slope
Intersection of solid and liquid curves in Gm vs T graph
Transition point: Melting Point
Intersection of liquid and gas curves in Gm vs T graph
transition temp: boiling point
Gm and stability relationship
Lower Gm, More stable
Most stable below melting point, Tm
solid
Most stable between Tm and Tb
liquid
Most stable above boiling point Tb
gas
At constant temperature, dGm/dP = ?
Vm
Shift of solid and liquid curves when decreasing pressure is
small decrease
Melting point ___ while boiling point ___ when pressure is decreased.
MP: changes very little
BP: significant decrease
____ pressure by applying vacuum ____ temperature need to ____ solvents
decreasing pressure
decreases temperature
evaporate solvent
Pressure and temperature at which all solid, liquid, and gas curves intersect
Triple Point
(T/F): Triple point is a characteristic of a substance
True
For select substances, there exists a pressure at which the gas curve is shifted in such way that at certain temperature, …
gas is more stable than solid
solid to gas:
gas to solid:
sublimation
deposition
shows the most stable phase at given temperature and pressure
phase diagram
Why solid-liquid curve of water slants to the left?
density of solid water is less than liquid water
Clapeyron Equation and what it describes
∆Sm/∆Vm = dP/dT
describes transformation of substances from one phase to another
For fusion, change in P = ?
∆P=(∆Hfusion / ∆Vfusion)(∆T/Tm*)
Tm* = ref transition temp
Clausius-Clapeyron Equation
∆Sm/Vm, gas = dP/dT
For vaporization and sublimation, the expression is?
ln P/P0 = - (∆Htransition/R)(1/T - 1/T0)
Phase Rule by J.W Gibbs
measures the degree of freedom (variance) of a system
number of variables needed to describe the state of system
F = Componemt - Phases + 2
____ Classification of Phase Transition
Ehrenfest
Most common phase transition
First-order
For first-order transitions, the first derivative plot of chemical potential against temperature (__vs__) is ___ at transition temperature
Sm vs T; discontinuous
____ change in entropy for first order transition since___
abrupt; heat is required to break bonds during phase transition at transition temperature
discontinuity appear at ____ of chemical potential vs temperature (____)
second derivative
Cp, m vs T
Second order transitions is common for
superconducting metals
___ change in entropy for second order transition since ___
no change
no bond breaking occur, only change in molecular symmetry
The ___ plot is lambda shaped
Cp,m vs T
second derivative of chem pot vs T
Lambda transitions are for ___
paramagnetic- ferromagnetic transitions
molecular transformation occurs ___ rather than abruptly in lambda transition
gradually
(T/F): heating absorbs KE before transition point
False; heating increases KE before transition point
at transition point, heat is ____ to ___
absorbed to break IMF between molecules
at transition point, there is ___ in temperature and KE
no increase
Heat capacity is in ____ at transition point
infinity
When will temperature increases again after transition point?
When additional input of energy once transition from one phase to another is complete
heat absorbed during transition
latent heat or enthalpy of transition
(T/F): latent heat increases with KE
False. It increases PE of substance
Why iodine does not really sublimes at ambient pressure?
Sublimation can only occur at 0.12 atm based on phase diagram
It will go from solid to liquid before liquid to gas
Why iodine emits vapor at ambient pressure?
iodine has low vapor pressure
vapors are highly colored that even small amounts can be visible
