Estimate the enthalpy change associated with converting orthorhombic to monoclinic sulfur at 368 K. 2) There is a triple point (triple phase coexistence between monoclinic, orthorhombic, and liquid sulfur) at about 427 K. Estimate the pressure at this triple point.
Io is a large moon of Jupiter. Io experiences a wide range of temperatures (as high as 1300 K and as low as 130 K), but its average temperature is about 140 K, for which it can snow sulfur. The Galileo spacecraft has detected sulfur on the surface of Io in huge amounts. Sulfur can take on several solid forms, including a monoclinic phase m and an orthorhombic phase o.
The monoclinic and orthorhombic sulfur undergo a phase transition at T = 368 K and P = 1 bar = 106 N/m2
The pressure on Io is quite low (less than 1 bar), but properties of solids are usually not strong functions of the pressure.
The molar entropy of the orthorhombic phase is so ≈ 10 + 7/100T J/(mol K)
The molar entropy of the monoclinic phase is sm ≈ 14 + 6.5/100T J/(mol K)
The molar volume of orthorhombic sulfur is vo = 15.4 cm3/mol at 298 K and 1 bar
The molar volume of monoclinic sulfur is vm = 16.2 cm3/mol at 298 K and 1 bar
1) Estimate the enthalpy change associated with converting orthorhombic to monoclinic sulfur at 368 K.
2) There is a triple point (triple phase coexistence between monoclinic, orthorhombic, and liquid sulfur) at about 427 K. Estimate the pressure at this triple point.
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