# Excess Enthalpy and Heat Capacity for an Ethanol-Water Mixture

Excess Enthalpy and Heat Capacity for an Ethanol-Water Mixture

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 =x(1-x)(T)+(T)+(T)+(T)+(T), where is the temperature and is the ethanol mole fraction. The excess heat capacity is given by ==x(1-x)++++. Finally, (T)=+T+, where and , , and are appropriate constants tabulated in [1].

E

H

a

0

a

0.5

0.5

x

a

1.5

1.5

x

a

2.5

2.5

x

a

4.5

4.5

x

T

x

E

C

P

∂

E

H

∂T

P

d(T)

a

0

dT

d(T)

a

0.5

dT

0.5

x

d(T)

a

1.5

dT

1.5

x

d(T)

a

2.5

dT

2.5

x

d(T)

a

4.5

dT

4.5

x

a

m

b

m

c

m

d

m

2

T

m=0,0.5,1.5,2.5,4.5

b

m

c

m

d

m

This Demonstration plots both excess properties versus ethanol mole fraction for user-selected values of temperature.