Bubble
Point: The bubble point of a system at pressure P
and whose liquid composition is given by mole fraction x_{i} is
that temperature at which there is onset of vaporization. Mathematically it is the temperature such
that
_{} |
For
a binary mixture, this equation can be rearranged to yield
_{} |
Example
6.2: Calculate the composition of a liquid of an
ideal binary mixture of benzene and toluene at 760 mm Hg at a bubble point of
90 °C. The following data apply:
Vapor pressure
of benzene = 1.02´10^{3}
mm Hg
Vapor pressure
of toluene = 225.1 mm Hg
Solution: At boiling point vapor pressure is equal to
the total pressure. Using this
definition, boiling point of benzene and toluene can be found to be 80.1 °C, and 130.13 °C,
respectively. The bubble point of a
mixture can be found from Equation 6.7
_{} |
x can be found
by using Equation 6.8
_{} |
The
results are summarized below:
t/°C |
P_{1}/ (mm Hg) |
P_{2}/ (mm Hg) |
K_{1} |
K_{2} |
x |
90 |
1.02´10^{3} |
225.1 |
1.34 |
0.296 |
0.672 |