Which of the following definitions best describes the term
"equilibrium line"?
A. A substance at conditions above its critical
temperature and pressure, where the liquid and vapor phases are
indistinguishable and have some characteristics of both a liquid
and a gas
B. The temperature and pressure at which all three phases
of a substance coexist. Under these conditions, freezing and
melting, boiling and liquefaction and sublimation and deposition
all proceed at the same rate.
C. Pressure and temperature values on a phase diagram
where two phases of a substance coexist
D. A specific temperature and pressure at which the liquid
and gas phases of a substance have the same density and are
indistinguishable from each other
E. In equilibrium with the liquid phase, the pressure
exerted by a gas