Which allotropic form of sulfur is the most thermodynamically stable at high pressures?
Rhombic sulfur
Monoclinic sulfur
Amorphous sulfur
Plastic sulfur
Option B At high pressures, above 100,000 atm, sulfur undergoes a phase transition from rhombic sulfur to monoclinic sulfur, which is the most thermodynamically stable form of sulfur at these high pressures. The transition is reversible, meaning that if the pressure is decreased, the monoclinic sulfur will transform back into rhombic sulfur.
Explanation of incorrect option
Incorrect Option A Rhombic sulfur is incorrect because while it is a stable form of sulfur at normal conditions, it is not the most stable form of sulfur at high pressures. Rhombic sulfur is a yellow, crystalline form of sulfur that exists at room temperature and pressure, but it transforms into monoclinic sulfur above 100,000 atm.
Incorrect Option C Amorphous sulfur is incorrect because it is a metastable form of sulfur that lacks a well-defined crystal structure. While it is stable under certain conditions, it is not the most stable form of sulfur at high pressures.
Incorrect Option D Plastic sulfur is incorrect because it is a metastable form of sulfur that is obtained by heating sulfur above its melting point and then cooling it rapidly. It is not the most stable form of sulfur at any pressure or temperature.