Question

Tin can exist as two stable allotropes: beta tin or white tin, which is metallic, and alpha tin or grey tin, which is non-metallic. At what tempterature will the conversion from one form to the other take place, that is, at what temperature will the two forms of tin be at equilibrium?

Sn(s, white) Delta Hf(kJ/mol)=0 Sknot (J/Kxmol)= 51.4

Sn(s, gray) Delta Hf(kJ/mol) = -2.09 Snot (J/Kxmol)= 44.1

Answer 1

Sn(white) ---------> Sn(gray)

H   = Hf products - H f reactants

         = -2.09 - = -2.09 Kj

S    = Sf products - Sf reactants

            = 44.1 -51.4 = -7.3J/mole-K    = -0.0073KJ/mole-K

S = H/T

-0.0073 = -2.09/T

T          = 2.09/0.0073   = 286.3K >>>answer