WOLFRAM|DEMONSTRATIONS PROJECT

Excess Enthalpy and Heat Capacity for an Ethanol-Water Mixture

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excess enthalpy
excess heat capacity
temperature in Kelvin
323.15
Consider a binary mixture of ethanol and water. Expressions for the excess enthalpy (in J/mol) and heat capacity (in J/mol·K) have been determined for this binary liquid system for the temperature range 298.15 K to 383.15 K by fitting experimental data to an empirical equation [1].
This equation for the excess enthalpy is
E
H
=x(1-x)
a
0
(T)+
a
0.5
(T)
0.5
x
+
a
1.5
(T)
1.5
x
+
a
2.5
(T)
2.5
x
+
a
4.5
(T)
4.5
x

, where
T
is the temperature and
x
is the ethanol mole fraction. The excess heat capacity is given by
E
C
P
=
∂
E
H
∂T
P
=x(1-x)
d
a
0
(T)
dT
+
d
a
0.5
(T)
dT
0.5
x
+
d
a
1.5
(T)
dT
1.5
x
+
d
a
2.5
(T)
dT
2.5
x
+
d
a
4.5
(T)
dT
4.5
x
. Finally,
a
m
(T)=
b
m
+
c
m
T+
d
m
2
T
, where
m=0,0.5,1.5,2.5,4.5
and
b
m
,
c
m
, and
d
m
are appropriate constants tabulated in [1].
This Demonstration plots both excess properties versus ethanol mole fraction for user-selected values of temperature.