Peng-Robinson Equation of State for Mixtures

temperature (K)

391

n-butane liquid mole fraction

x

1

0.97

This Demonstration studies the vapor-liquid equilibrium for a binary mixture of

n

-butane(1) and

n

-octane(2) by plotting isotherms on a log pressure versus log volume graph. The isotherms are calculated using the Peng–Robinson equation of state for mixtures. Use the sliders to select the temperature and the mole fraction

x

1

of the liquid. The mole fraction of the vapor

y

1

and the equilibrium pressure are calculated from Raoult's law and are displayed in the upper-right corner along with

x

1

. The dashed black line connects the liquid mole fraction on the blue isotherm to the vapor mole fraction on the green isotherm.