236 5 Phase Equilibrium
f.The Clausius–Clapeyron equation can be used for a
solid–liquid phase transition.
g.The Clapeyron equation cannot be used for a
liquid–vapor phase transition.
h.The surface tension of liquid water is greater than that
of liquid benzene because the intermolecular attraction
of water molecules is larger than that of benzene, due to
hydrogen bonding.
i.It is impossible for four phases of a single substance to
coexist at equilibrium.
j.It is impossible for four phases of a mixture of two
components to coexist at equilibrium.
k.The maximum number of phases in a system of four
components is equal to six.l.Two phases at equilibrium must have the same
temperature.5.54 The stable crystalline form of sulfur at room temperature is
called rhombic sulfur, and another crystalline form is
called monoclinic sulfur. The standard-state enthalpy
change of formation of monoclinic sulfur at
298 .15 K is 0.33 kJ mol−^1 , and the standard-state
Gibbs energy change of formation of monoclinic
sulfur is 0.096 kJ mol−^1. Assume that both∆H◦
and∆G◦for the conversion of rhombic sulfur to
monoclinic sulfur are temperature-independent.
Estimate the temperature of coexistence of these
rhombic sulfur and monoclinic sulfur at standard
pressure. Compare your result with the experimental
temperature, 95◦C.