Tin exists in two solid forms, white and gray tin. While white tin has a bodycentered tetragonal structure, the structure of gray tin is diamond cubic. The enthalpy and entropy changes associated with the transformation of gray tin to white tin at 298 K and atmospheric pressure are 2090 J/mol and 7.3 J/mol K, respectively.
a) Which form of tin is the more stable at 298 K?
b) Under atmospheric pressure, estimate the temperature at which white and gray tin coexist in equilibrium. Indicate your assumptions.