generalization of ideal gas behavior_2
TRANSCRIPT
-
8/3/2019 Generalization of Ideal Gas Behavior_2
1/27
Generalization of Ideal Gas Behavior
Boyles Law
The volume of any definite quantity of
gas at constant temperature varied
inversely as the pressure on the gas.
P1V1 = P2V2
Charles Law
The volume of a definite quantity of
gas at constant pressure is directly
proportional to the absolute temperature.
Gay-Lussacs Law
Combined Gas Law
Avogadros Law
Ideal Gas Equation
PV = nRT
Values of R:
0.08205 L-atm/mol-K
82.05 cc-atm/mol-K
8.314 x 107 ergs/mol-K
8.314 J/mol-K
1.987 cal/mol-K
62360 mmHg/mol-K
Daltons Law of Partial pressure
At constant temperature, the total
pressure exerted by a mixture of gases in a
definite volume is equal to the sum of the
individual pressure without each gases
would exert if it occupied the same total
volume alone.
PT = P1 + P2 + P3 + +Pn
Partial pressures:
P1 = P2 =
P3 =
-
8/3/2019 Generalization of Ideal Gas Behavior_2
2/27
Daltons Law:
PT =
PT = nT
Partial Pressure of a gas to the total
pressure of the mixture:
P1 =
P2 =
P3 =
PA/PT = nA/nT = NA (mole fraction)
PB/PT = nB/nT = NB (mole fraction)
PC/PT = nC/nT = NC (mole fraction)
NA + NB + NC = 1
Amagats Law of Partial Pressure
In any gas mixture the total volume
may be considered to be the sum of the
partial volumes of the constituents of the
mixture.
VT = V1 + V2 + V3 + + Vn
V = (n1 + n2 + n3)
V = nT
VA/V = NA/RT = NA
VB/V = NB/RT = NB
VC/V = N
C/R
T= N
C
Graham's Law of Diffusion
At constant temperature and pressure,
the rate of diffusion of various gases
varies inversely as the square roots of
their densities or molecular weights.
=
=
Where:
u or r = rate of diffusion
p1 or p2 = densities
Limitation of Ideal Gas
Low to moderate pressurePV = znRT
Where:
z = compressibility factor
If: z > 1 = dominant adhesive force
z < 1 = dominant cohesive force
-
8/3/2019 Generalization of Ideal Gas Behavior_2
3/27
Van Der Walls Equation of State
Van Der Walls deduced that the
magnitude of the pressure correction P' for
n moles of gas present in volume V is given
by:
P' = where a is a constant
Thus:
(P +
(V-nb) = nRT
Note: valid only for wide pressure range
a =
b =
Kamerlingh Onnes Equation of State
PV seriesPVm = A + BP + BP2 + BP3 +
Where:
P = pressure
Vm = molar volume
A,B,C = viral coefficients
Rate: PVM = A
PV2 = nRT
Berthelot Equation
PV = nRT (1 +
Where: T = actual temperature
Tc = critical temperature
P = actual pressure
Pc = critical pressure
Beattie - Bridgeman Equation of State
P =
Vm =
Where:
= RTB0 - A0 -
= -RTB0b + Aoa -
=
T = absolute temperature
R = gas constant
Ao, Bo, a, b, c = constant
characteristic of each gas
-
8/3/2019 Generalization of Ideal Gas Behavior_2
4/27
Molecular Weights of Gases
p = p =
MW = M =
Some Methods for Determination of Molecular
Weights
Regnult's Method
> employed to determine the molecular
weights of substances which are gaseous at
room temperature.
Dumas' Method
> used to determine molecular weights
in the vapor phase of readily volatile
liquids.
Wvapor = W(bulb + vapor) - W(bulb + air) + Wair
M =
[1 +
(1- )] (Berthelot
Equation)
Determination of ExactMolecular Weights
Method of limiting densities
> based upon the fact that as zero
pressure is approached, the ideal gas laws
become the exact for all gases
PMW = pRT
p/P = MW/RT = constant
(p/P)P=0 = MW/RT
MW = RT P=0
Plotting:
P (atm)
Kinetic Theory of Ideal Gases
The Kinetic Theory is based on the
following fundamental postulates:
1. Gases are considered to be composed of
minute discrete particles called molecules.
-
8/3/2019 Generalization of Ideal Gas Behavior_2
5/27
For any one gas all molecules are thought
to be of the same mass and size but to
differ in these from gas to gas.
2. The molecules within a container are
believed to be in ceaseless chaotic motion
during which they collide with each other
and with the walls of the container.
3. The bombardment of the contaiuner walls
by the molecules gives rise to thephenomenon we call pressure (force/unit
area).
4. In as much as the pressure of the gas
within a container does not vary with time
at any given pressure and temperature. The
molecular collisions must involve no energy
loss due to friction. In other words, allmolecular collisions are elastic.
5. The absolute temperature is a quantity
proportional to the average kinetic energy
of all the molecules in a system.
6. At relative low pressures, the average
distances between molecules are largecompared with the molecular diameters, and
hence the attractive forces between
molecules, which depend on the distance of
molecular separation, may be considered
negligible.
7. Finally, since the molecules are small
compared with the distances between them,
their volume may be considered to benegligible compared with the total volume
of the gas.
Root-Mean-Square Velocity
U =
= Where:
U = root-mean-square velocity
Ux, Uy, Uz = component velocities along
x, y, or z
Momentum = mass x velocity (mu)
Change in momentum
m = m1 - m2
= mux - (-mux) = 2mux
Change in Momentum per Second per Moleccule
= (2mux) =
= 2
Total change in momentum/molecule/second =
2
+ 2
+ 2
-
8/3/2019 Generalization of Ideal Gas Behavior_2
6/27
= (U
2x + U2y + U2z)
= U2
For n' molecules in a cube
Total change in momentum per second =
P = =
P = =
=
PV = mn'
Where:
A cube = 6l2
F =
V = l3
Deductions from Kinetic Theory of Gases
Boyle's Law
1/2 mn'U2 = K1T
1/2 PV = 1/3 K1T
PV = 2/3 K1T
PV = C
V/T = C'
P/T = C"
Charle's Law
V = T
V = K2T
Avogadro's Principle
> equal volumes of all gases at the same
pressure and temperature contain equal
numbers of molecules
For two gases
P1V1 = P2V2
1/3 n'1m1= 1/3 n'2m2
m1 = m2
per mole
1/3 n'1m1= 1/3 n'2m2
n'1 = n'2
n' = n x avogadros number
where:
n = moles
n' = molecular wt
-
8/3/2019 Generalization of Ideal Gas Behavior_2
7/27
N'1 = N'2 (no of molecule will be the
same)
Avogadro's No (N) = 6.023x1023 molecules/gram-
mole
Graham's Law of Diffusion
PV = C
P1V1 = P2V2
1/3 n'1m1= 1/3 n'2m2
U21/ U22 =
U1/ U2 = =
U1/ U2 = = =
PV = nRT
PV = 1/3 n'mu2 = nRT
PV = = nRT
Where:
n' = nM
n' = no of molecules
n = avogadro's number
Further Deduction from the Kinetic Theory
Velocity of Gas Molecules
> 1/3 nMWU2 = nRT
U2 =
U =
= Kinetic Energy of Translation
Ek =(
nMu
2)
=nRT
Where:
nRT =
MWU2 = 3RT
On division by Avogadro's no.
Ek/N =
= kT
Where:
K = is called the Boltzman constant
and is equal to 1.3805 x 10-16 erg per
degree
-
8/3/2019 Generalization of Ideal Gas Behavior_2
8/27
Distribution of Molecular Velocities
Maxwell-Boltzman Distribution Law
dnc/n' = 4(
)3/2 e-MC2/2RT c2dc
dividing by dc:
P =
= 4(
)
3/2 e-MC2/2RT c2dc
W
here:
P = probability of finding molecules
with the velocity
dnc = no of molecules out of a total
n' having velocities between c and c + dc
M = molecular wt
T = temeperature of gas
Dnc/n' = fraction of the total number of
molecules having the same velocities
Most Probable Velocity ()
= Average Velocity (v)
= v = 0.912u
v = 0.921 where:
:v:u = 1:1.128:1.224
Frequency of Collisions and Mean Free Path
> the number of molecules which a single
gas molecule will collide per second is:
v2(n*)2
Where:
v = average velocity in cm per second
= molecular diameter in cm
n* = n x (6.023 x 1023)
Z = v2(n*)2
Z = total no of colliding molecules per cc
per second
Nc = no of molecular collisions occurring
in each cc per second
Nc =
=
v
2(n*)2
-
8/3/2019 Generalization of Ideal Gas Behavior_2
9/27
Mean Free Path (l)
> the average distance a molecule traverse
before colliding
l =
Heat Capacity of Gases
Cp = at constant pressure
Cv = at constant volume
Ek = RT
E = Ek2 - Ek1 =R(T2 -T1)
Cp - Cv =
Cv = R
Cp = R
H = E + PV
Specific Heat Ratio
For monoatomic gases:
= =
= = 1.667
For diatomic gases: (H2, N2, O2 I2 Cl2)
Cp - Cv = R Cp = 7/2 R
Cv = 5/2 R = 1.4
For triatomic gases: (CO2, SO2, H2S N2O)
= 1.3
Theory of Non-Ideal Gases
Interaction energy (E')
E' = - +
Force interaction (f')
f' = -
where:
A and B are constant molecule
r = distance of separation
n = constant whose value may range from
9 12
-
8/3/2019 Generalization of Ideal Gas Behavior_2
10/27
LIQUIDS
Critical Phenomena in Liquids
> properties of liquids and vapor become
identical
> critical points are:
Critical Temperature, Tc
Critical Pressure, Pc
Critical Volume, Vc
For H2O critical constants are:
Tc = 374.4C
Pc = 219.5 atm
Vc = 58.7 cc per mole
Liquefaction of Gases
Process involve: cooling
Cooling + compressor
For permanent gases:
Adiabatic expansion, Q = 0
Allowing gas to cool itself by performing
work in adiabatic expansion against piston.
Viscosity
> resistance to flow and produce by
shearing effect of moving one layer of
fluid past, another and quite distinct from
intermolecular attraction.
Fluidity > opposite of viscosity
=
Where:
=
= viscosity on absolute
dynamic
Kinematic Viscosity
Viscosity of Gases
= vlp
where:
p = density
l = mean free path
l =
-
8/3/2019 Generalization of Ideal Gas Behavior_2
11/27
Poiseville or Stokes Equation
=
1/2 =
Where:
P = pressure
t = time of flow
r = radius of tube
V = volume of liquid
Stoke's Law
> applicable to the fall of spherical
bodies in all types of fluid media provided
the radius of the falling body is large
compared with the distance between the
molecules of the fluid.
W = m g/gc
W = PV g/gc
F1 = 4/3 r3(p - pm)g/gc
F2 = 6rv
Equating F1 and F2:
4/3 r3(p - pm)g/gc = 6rv
=
Fluidity ()
=
1/2 =
> the viscosity of liquid decreases withincreasing temperature
Fg = F1
FR = F2
-
8/3/2019 Generalization of Ideal Gas Behavior_2
12/27
First Law of Thermodynamics
Thermodynamics = study of energy conversion
Kinds of Energy
> Kinematic Energy
The energy a system possesses by
virtue of its motion
> Potential Energy
The energy a system possesses by
virtue of its position
Mechanical energy > erg (cgs)
Electrical energy > joule (cgs)
Thermal energy > calorie (cgs)
Thermodynamic System
System
> anything under study or consideration
> as any portion of the universe isolated
on or in an inert container, which maybe
real or imaginary, for purposes of study of
the effect of various variables upon the
contents of the system.
A system can be:
Open System
> flow of energy, flow of mass (pump)
> a system which can exchange both matter
and energy with its surroundings
Closed System
> no mass flow, flow of energy (elec bulb)
> one which no transfer of matter to or
from the surroundings is possible, but that
of energy is
Isolated System
> no mass flow(transfer): no energy flow
> one which cannot exchanged both matter
and energy with its surroundings
It can be:
Homogeneous System = contains only one
phase
Heterogeneous System = two or more
than a single phase may involved
-
8/3/2019 Generalization of Ideal Gas Behavior_2
13/27
Phase
> defined as homogeneous, physically
distinct, and mechanically separable
portion of a system.
Steady State
> does not change in time
True Solution
> physically homogeneous mixture of two or
more substances
Thermodynamics SystemProperties:
Extensive property
> dependent on the mass
Intensive Property
> mass independent
First Law of Thermodynamics
Energy can neither be created nor
destroyed but it can only transform from
one form to another.
PE1 + KE1 + E1 + P1V1 + Q = W + P2V2 + KE2 +E2 +
P2V2
First Law Equation:
E = q - W
dW = fdl = pAdl
W =
Wmax is attained at reversible process
W = (+) work is done by the system (V2 > V1)
expansion
W = (-) work is done on the system (V2 < V1)
compression
q = (+) absorbed
q = (-) evolved
E = q - p(V2 - V1)
a. P is constant
E = q - p(V2 - V1)
b. Volume is constant
E = q
c. free expansion
P = 0; W = 0
E = q
-
8/3/2019 Generalization of Ideal Gas Behavior_2
14/27
d. P is variable, T is constant
W = nRT ln
W = nRT ln
Enthalpy of a System
H = E + PV
H = H2 - H1
= (E2 + P2V2) - (E1 + P1V1)
= (E2 - E1) + (P2V2 - P1V1)
= E + P(V2 - V1)
H = E + PV
Where:
E = internal energy
If Cp = f(T)
Cp = a + bT + CT2 + dT3
Cp = a + b/T2 + C/T2
H = n
At constant volume:
C =
Cv = (
v
=
E =
E = mCvT
H = E
H = (E2 - E1) + (P2V2 - P1V1)
H = E + Pv
H = q - PV + PV
H = q
H > E if w = 0, w > 0
H = E if w = 0
H = (+) absorption of heat
H = (-) evolution of heat
0
-
8/3/2019 Generalization of Ideal Gas Behavior_2
15/27
Heat Capacity (Cp, Cv)
Cp = heat capacity at constant temperature
W = rate of change of the internal energy
with temperature at constant volume.
Cp = (
v
At constant pressure:
Cp = (
P
If Cp is constant:
H = nCpT
=
H = when n = 1
H = when n = 1
H = E + PV
Differentiating it with respect to
temperature at constant pressure:
Cp - Cv = ()P + P(
) - (
)v
Difference of state of state function on
variables:
*E as a function of (T, V) then:
E = f(T,V)
*H = f(T,P)
dH = CpdT + [V - T()P]dP
Thermodynamics Behavior of Ideal Gas
PV = nRT
For ideal gas:
Cp - Cv = nR
Cp - Cv = R
For monoatomic gases:
Cp = 5/2 R
Cv = 3/2 R
For diatoimic gases:
Cp = 7/2 R
Cv = 5/2 R
Note:
=
-
8/3/2019 Generalization of Ideal Gas Behavior_2
16/27
For monoatomic = 1.6
For diatomic = 1.4
For triatomic = 1.3
Isothermal andAdiabatic Process
Isothermal Processes
> any process conducted in a manner such
that the temperature remains constant
during the entire operation.
E = q - w
0 = q - w
q = w
Isothermal process in ideal gas
W = nRT ln V2/V1
W = nRT ln P1/P2
If P is constant:
W = P(V2 - V1)
Adiabatic process in ideal gas
q = 0 (no heat evolved nor absorbed)
E = - w
w = - E
Where:
E =
* Gas laws are not applicable in adiabatic
process.
Derived formula:
P1V1 = P2V2
= ( )
= (
= (
w =
w =
Joule - Thompson Effect
Adiabatic:E = - w
E2 - E1 = (P2V2 - P1V1)
E2 + P2V2 = E1 + P1V1
H2 = H1
H = 0
-
8/3/2019 Generalization of Ideal Gas Behavior_2
17/27
Joule - Thomson Coefficient:
=()H
Cp = - ()T
Cp = T ()P - V
Where:
Cp = ()P
= 0 at inversion point (gas
neither heat or cools)= (+) cooling
= (-) heating
The Carnot Cycle
> in itial and final states are equal
> composed of several steps/processes
Carnot Cycle Steps
> 2 isothermal (T = C) process (expansion,
compression)
> 2 adiabatic process (q = 0) (expansion,
compression)
Analysis of the cycle
1. AB --- isothermal expansion
E = q2 - w1
E = 0
q2 = w1 = nRT2 lnV1/V2 = nRT lnP2/P1
w = q2 - q1
2. BC --- adiabatic expansion
q = 0
E = - w2
E =
3. CD --- isothermal compression
E3 = 0
E3 = -q1 - w3
q1 = -w3 = -nRT lnV4/V3
4. DA --- adiabatic compression
q = 0
E4 = -w4
E4 =
E cycle = 0
w max = q2 - q1
P
V
Isothermal
Expansion
AdiabaticExpansion
Isothermal
Compression
Adiabatic
Compression P1V1
P2V2
P3V3
P4V4
A
B
C
D
-
8/3/2019 Generalization of Ideal Gas Behavior_2
18/27
Thermodynamics Efficiency
Eff =
x 100Eff =
=
=
= x 100
=
x 100
ThermoChemistry
> branch of physical chemistry which deals
with the thermal changes accompanying
chemical and physical transformation.
Heat lost = heat gained
qH = mCpT
Heat of ReaCTION AT Constant Volume or
Pressure
E = q - w
q = E +
at constant volume: V = 0q = E
at constant pressure:
q = H
where:
H + E = (+) heat is absorbed
H + E = (-) heat is evolved
Calculation of E fromH or vice versa
H = E + PV
= E + (PVP - PVR)
= E + (npRT -nRRT)
= E + (NP -NR) RT
H = E + ngRT
Where: ng = nP - nR
Hess' Law of Heat Summation
> the heat of reaction must be independent
of the particular manner in which the
reaction takes place
Heat of Combustion
> for combustible material
> amount of heat liberated per mole of
substance burned
Hrxn =
Heat of Formation
> heat involved in the formation of 1 mole
of substance from the element.
Kirchhoff's Equation
Cp = CpP - CpR
Cp = [
]P
E2 =
-
8/3/2019 Generalization of Ideal Gas Behavior_2
19/27
The Second and Third Law of Thermodynamics
> The flow of heat is unidirectional,always from higher temperature region to
lower temperature region.
> All naturally occurring process always
tend to change spontaneous in a direction
which will land to equilibrium.
> Heat cannot be converted to work which
leaving permanent changes either in systems
involved or in their surroundings.
Haber Process
Entropy
> degree of disorder
> state of a function> depends only on initial and final state
of the system
S = S2 - S1
dS =
where dq = infinite quantity of heat
At constant temperature:
=
S =
Entropy Change in Isolated Systems
Reversible expansion:
Ss =
Sr =
V1 - V2 System = Ss + Sr
= +
System = 0
Isolated System Under Non-Isothermal
Condition Founds:
> for any reversible process or cycle S =
0
> for any irreversible process or cycle
S = ; S > 0
The Second Law of Thermodynamics
> All process in nature tend to occur only
with an increase in entropy and that the
directions of change is always such as to
the entropy increase.
dsi > 0
T2
q2
q1
W
q2 = q1 + W
-
8/3/2019 Generalization of Ideal Gas Behavior_2
20/27
Entropy Change for Systems Only
ds = ds + dsr > 0system + reservoir
dsr =
ds + dsr > 0 E = q - w
ds - > 0 dE = dq - dw
Tds - dq > 0 dq = dE + dw
Tds - dE - pdV -dw' > 0
For irreversible process
Tds - dE - PdV - dw' > 0
PV = nRT P = P1 dw' = dw'mTds - dE - PdV - dw;mx = 0
Tds - dE - PdV = 0
Entropy Change in Ideal Gases
Isothermal
dE = 0Tds = PdV
ds =
ds =
=
In Isolated System
S = nRln
S = nRln
S = -nRln
Dependence on Temperature andVolume
ds = (
)v dT + (
)T dV
= dT +
)vdV
S = nCv ln
+ nR ln
S = f (T,P)
S = ncP ln
+ nR ln
Entropy of Mixing for Ideal Gas
Sm = n1R ln
+ n2R ln
Sm = n1R ln
+ n2R ln
If
=
= PT (special cases)
Sm = - (n1RlnN1 + n2RlnN2)
-
8/3/2019 Generalization of Ideal Gas Behavior_2
21/27
Entropy Change in Physical Transformations
S = S2 - S1
S = =
where: Hv = latent heat
q = Hv = Hf = Hs
Hs = Hv + Hf
L - G S =
(evaporation)
G - L S = (cooling)S - L S =
(melting)
S - G S = =
(sublimation)
q = sensible heat
q = mCpT
Change Entropy in Chemical Reactions
A + bB + = cC + dD +
S = -
S = ;
=
S2 = S1 + nCpln
if cP is constant
Third Law of Thermodynamics
-
ST =
ST =
Free Energy and Equilibrium
> capability of the rxn to do work
Helholtz Free Energy (A)
A = E - TS
At constant temperature:
A = A2 -A1
= (E2 -TS2) - (E1 - TS1)
= E - T(S2 - S1)
A = E - T(S)
If T is not constant:
A = (E2 -TS2) - (E1 - TS1)
= E - (T2S2 - T1S1)
A = E - TS
S =
qr = TS
At constant temperature:
A = E - TS
= E - qr
= - wWmax = -A
Where: in first law of thermodynamics
E = q - w
E - q = - w
At constant temperature; ideal gas
W = nRT ln
= nRT ln
-
8/3/2019 Generalization of Ideal Gas Behavior_2
22/27
A for Reactions
A = E - TS
dA = dE - (TdS + SdT)
A = f (T,V)
a) dA = ()vdT + (
)dV
b) dA = dE - TdS - SdT
= dE - SdT - dqr
Where:
dqr = dE + dw
dqr = dE + pfV
dA = dE - SdT - (dE + pdV)
dA = - SdT - pdV
Where:
-S = (
)v A = E - TS
-P = ()T
Therefore:
()v =
=
(
)v = -
()v =
dT
Where:
E = f(T)
E =
()v =
dT
The Gibbs Free Energy (G)
G = H - TS
G = G2 -G1
G = H - TS if T is constant
G = H - qr
= E + PV - qr
= E - qr + PV
= A + PV
G = A + PVG = - (Wm - PV)
Where:
A = f (T,V)
G = f (T,P)
G1 = (H1 - T1S1) = G2
G = A + PV
S =
A = - w
E = q - w
E - q = A
G = f (T, P)
dG = VdP - SdT
[
]P =
=
=
(
) =
-
8/3/2019 Generalization of Ideal Gas Behavior_2
23/27
Where:
-S = ()P
V = ()T
G = H - TS
H = G + TS
( )P = - S
(
) =
Properties and Significance of G
AT constant T, P:
G = 0 @ equilibrium
G = - spontaneous
G = + non - spontaneous
G = H - TS
G = H - qr
qr = H - G
qr (+) = H >G (absorbed)
qr (-) = G >H (evolved)
Calculations of Free Energy Changes
At constant temperature:
G = VP if V is constant
If V = f (T) ; ideal gas
G = nRT ln
G = nRT ln
Fugacity andActivity Concepts
G = RT lnf + B
At standard state:
G0 = RTlnf0 + B
G = G0 + nRT ln f/f0
G = G0 + 1
G = G0
Per Mole:
G = nRT ln
Where:
f/f0 = a
a = 1
Standard State for Gases
Where:
f0 = 1 f = P as P = 0
a = f/f0 lim
= 1
a = f P-0
G = G0 + RT lnf
= (activity coefficient)
ideal gas
Determination of Activity Coefficients of
Gases
dG = VdP ; G = VP
G = G0 + RT lnf
-
8/3/2019 Generalization of Ideal Gas Behavior_2
24/27
dG = RTdlnf
dlnf =
dlnf =
= ( + )
= +
= dlnP +
Dlnf - dlnP =
W
here: = V -
V = +
=
dln
= dln =
=
lny = (P - 0)lny =
if T and is constant
Standard States for Solid and Liquids
> As the standard of pure solid or liquidis taken the solid or liquid at 1 atm
pressure at each temperatue.
a = 1
The Reaction Isotherm
A + bB cC + dD
GA = + RT ln aA
GB = + RT ln aB
GC = + RT ln aC
GD = + RT ln aD
Grxn =
-
= (cGC + dGP) - (GA + bGB)G = G0 + RT ln (ln /)
Criteria of Equilibrium
Where:
G = 0
H = E + PV
G = H - TS
TdS = dE - PdV = 0
If:
V = C ; E = C
dV = 0 ; dE = 0
Then:
TdS - 0 - 0 = 0
TdS = 0
dS = 0
(S)E,V = 0 at equilibrium
-
8/3/2019 Generalization of Ideal Gas Behavior_2
25/27
If:
T and V are constants
dA + 0 + 0 = 0(dA)T,V = 0
(A)T,V = 0
Then:
A = E - TS
dA = dE - TdS - SdT
TdS - dE = -dA - SdT
-dA - SdT -PdV = 0
dA - SdT - PdV = 0
3 Criteria of Equilibrium
(S)E,V = 0
(G)T,P = 0
(A)T,V = 0
AT constant T and P:dG + 0 - 0 = 0
(dG)T,P = 0
(G)T,P = 0
Then:
G = H - TS
= E + PV - TS
G = A + PV
dG = dA + PdV + VdP
dA + PdV = dG - VdP
-SdT = dG - VdP
dG + SdT - VdP = 0
where: A = E - TS
Physical equilibrium Involving Pure
Substances
At equilibrium:
dG = 0 dA = 0
dT = dP = 0 A = 0
G = 0 A2 - A1 = 0
G2 - G1 = 0 A2 = A1
G2 = G1
dG = -SdT + VdP = dG1 = dG2
-S2dT + V2dP = -S1dT + V1dP
(V2 - V1)dP = (S2 - S1)dT
dP/dT = (S2 - S1)/(V2 - V1) =
Where:
S = q/T ; q = H
S = H/T
Therefore: =
--- clayperon equation
Uses of Clayperon Equation
=
=
(
)
=
P2 - P1 = ln
-
8/3/2019 Generalization of Ideal Gas Behavior_2
26/27
The Boiling Point of Liquids
Liquid to Vapor (Evaporation/Condensation)
H = Hv =
=
Where:
V = Vg - VL
V = VgPV = nRT
Vg = nRT/P
By substitution: integration:
ln=
(
)
Solid to Liquid(Fusion)
H = Hf where: V = Vl - Vs =
By substitution: integration:
P2 - P1 = ln
Troutons Rule
= c = 21
Sublimation (Solid to Gas)
Hs = Hv + Hf
V = Vg - Vs =
=
By substitution and integration:
ln
=
(
)
where:
Vg >>> Vs
V = Vg
PV = nRT
V = nRT/P
-
8/3/2019 Generalization of Ideal Gas Behavior_2
27/27
PhysicalChemistry
I
Physical
Principles
Alfredo Samsona Jr.