Solthermo (Midterm) - Terms

System Boundary

A boundary is a closed surface surrounding a system through which energy and mass may enter or leave the system.

Surroundings

Everything that interacts with the system.

System

A system is a region containing energy and/or matter that is separated from its surroundings by arbitrarily imposed walls or boundaries

Surroundings

It encompasses to all other parameters
interacting with the system.

0 KJ

A gas is confined in a cylinder piston. The initial pressure of the
gas is 7 bar and the volume is 0.10 m3
. The piston is held in
place by latches in the cylinder wall. The whole apparatus is
places in a total vacuum. What is the energy change of the
apparatus if the latches are removed so that the gas suddenly
expands to double its initial volume, the piston striking other
latches at the end of the process?

INTERNAL ENERGY

The total of the kinetic
and potential energy
of particles.
∆U = ∫Cv dT;
∆U = n Cv (T2 - T1);
ΔU = Q + W

ENTHALPHY ENERGY

State function
representation of
heat content.
H=U+PV

HELMHOLTZ FREE ENERGY

In thermodynamics, the _________ is a thermodynamic
potential that estimates the useful
work available from a closed
thermodynamic system at a
constant temperature
A = U - TS

GIBBS FREE ENERGY

is a quantity
that is used to measure the
maximum amount of work done in
a thermodynamic system when
the temperature and pressure are
kept constant.
G = H - TS

GIBBS FREE ENERGY

ΔG > 0; the reaction is non-
spontaneous.
ΔG < 0; the reaction is spontaneous
ΔG = 0; the reaction is at equilibrium

Absolute
Temperature

The internal energy of an ideal gas
depends on:

U

A sample of an ideal gas has an internal energy of
U and is then compressed to 1⁄2 of its original
volume while the temperature stays the same.
What is the new internal energy of the ideal gas in
terms of U?

MASS FRACTION or MOLE FRACTION

is defined as the ratio of the mass or
number of moles of a particular chemical species in a
mixture to the total mass or number of moles of mixture

MOLAR CONCENTRATION

Ratio of the mole fraction of a particular chemical
species in a mixture or solution to the molar volume of
the mixture or solution.

MOLAR MASS OF SOLUTION

The mole-fraction-weighted sum of the molar masses
of all species

d(nG) = (nV)dP - (nS)dT
(CLOSED SYSTEM)

With the incorporation of the
number of moles for any closed
system.

d(nG) = (nV)dP − (nS)dT
dG=−S dT+ V dP
(OPEN SYSTEM)

* Material may pass into and
out of the system.
* nG becomes a function of
the numbers of moles of the
chemical species present.

Composition is necessarily
constant.
(CLOSED SYSTEM)

Single-phase fluid in a closed
system wherein no chemical
reactions occur.
composition is necessarily
constant.

SPECIAL CASE

one mole of solution, n = 1 and ni = xi

CLOSED SYSTEM
d(nG) = (nV)dP − (nS)dT

GENERALITY
d(nG) = (nV)dP − (nS)dT+Chemical Potential

For a closed, single-phase PVT system
containing chemically reactive species:

CLOSED SYSTEM
d(nG) = (nV)dP − (nS)dT

GENERALITY
d(nG) = (nV)dP − (nS)dT+Chemical Potential

PHASE EQUILIBRIUM
(closed nonreacting system)

For a closed nonreacting system consisting
of two phases in equilibrium, each
individual phase is open to the other, and
mass transfer between phases may occur.

TOTAL System Property

The change in the total Gibbs energy of the two-phase system is the
sum of the equations for the separate phases.

same T
and P are in EQUILIBRIUM when the
chemical potential of each
species is the same in all phases.

multiple phases at the same T
and P are in EQUILIBRIUM when the
chemical potential of each
species is the same in all phases.

partial molar property -Mi

Sometimes called as Response Function

partial molar property -Mi

It is a measure of the response of total
property nM to the addition of an infinitesimal
amount of species i to a finite amount of solution,
at constant T and P.

Partial Molar Properties

These properties are used for mixtures to indicate the
properties of individual compounds in a mixture, even
though the components are mixed on a molecular
scale.

partial molar property

provides the
means for calculation of partial properties from
solution property data.
The total thermodynamic properties of a
homogeneous phase are functions of T, P, and the
numbers of moles of the individual species that
comprise the phase.

Gibbs-Duhem equation

is a thermodynamic relationship that expresses
changes in the chemical potential of a substance in terms of changes in
temperature and pressure of the system. It involves the mole fraction and
the chemical potential, which measures the energy required to add a
molecule of a particular component to the system

ideal-gas-state mixture model

provides a
conceptual basis upon which to build the structure
of solution thermodynamics.

It is a useful property model because it:
• has a molecular basis;
• approximates reality in the well-defined limit of
zero pressure;
• is analytically simple

Reducing the
release of flames

Which can the air inside the air
balloon be brought into a more
ideal condition?

High Temperature
and Low Pressure

An ideal gas will only be considered
in which of the following
parameters?

Boyle's Law

Which Gas Law is involved when a
balloon pops after being sat on?

Flask 1

Each of these flasks contains the same
number of molecules. In which
container is the pressure highest?

HIGH TEMPERATURE and LOW PRESSURE
(PV=nRT)

Achieved at HIGH TEMPERATURE and LOW PRESSURE
in order to neglect the attractive and repulsive
forces between particles, as well as the volume of
the particle themselves.

MOLAR VOLUMES IN THE IDEAL GAS STATE

At deal-gas state at given T and P the
partial molar volume, the pure-species
molar volume, and the mixture molar
volume are identical.

PARTIAL PRESSURE, Pi

the pressure that species i would exert if it alone occupied
the molar volume of the mixture.where yi
is the mole fraction of species i.

MIXING AT IDEAL GAS STATE MIXTURE
(this enthalpy change of mixing is ZERO.)

the difference on the left is the enthalpy change
associated with a process in which appropriate amounts
of the pure species at T and P are mixed to form one
mole of mixture at the same T and P. For the ideal-gas
state, this enthalpy change of mixing is ZERO.

(Because 1/yi>1) always positive

this quantity is always POSITIVE, in
agreement with the second law. The mixing process is
inherently irreversible, so the mixing process must
increase the total entropy of the system and
surroundings together.

FUGACITY

is based on a Latin root
meaning to flee or escape, also the basis for the
word fugitive.

fugacity

has been interpreted to mean
"escaping tendency". When the escaping
tendency is the SAME for the two phases, they are
in EQUILIBRIUM.

higher in one phase
fugacity is
lower

When the escaping tendency of a species is
higher in one phase than another, that species will
tend to transfer to the phase where its fugacity is
lower.

IDEAL GAS
(Gig = (T) RT In P)

The origin of the fugacity
concept resides in the equation
below which is valid only for pure
species i in the ideal-gas state.

Real Gases
(Gig = (T) RT In fi)

For a real fluid, an analogous
equation that defines fi, the
fugacity of pure species i:

FUGACITY OF VLE OF PURE SPECIES

For a pure species, coexisting liquid and vapor phases are in
equilibrium when they have the same temperature, pressure,
and fugacity.

fugacity
coefficient of species i
in solution

The dimensionless ratio
is called the

partial
pressure

fugacity of species
i in an ideal-gas-state
mixture is equal to its partial
pressure.

mixture second virial coefficient B

is a function of
temperature and composition.

LEE KESLER CORRELATION

A useful generalized correlation for lnφ results when
the simplest form of the virial equation is valid.

kij

is an empirical interaction
parameter specific to an i - j
molecular pair. When i = j
and for chemically similar
species, kij=0.