For iodine the enthalpy of sublimation is 62.0 kJ/mol. The entropy of sublimation is 145 J/(K mol).?

Question

Calculate the sublimation temperature (Kelvin).

NOTE: the data given may not be from the Appendix. You need an equation that gives the unknown quantity in terms of the two given ones. Also entropy is usually reported in J/mol-k, while enthalpy usually reported in kJ/mole

Answer 1

The equation you need is DG = DH - TDS (where D = delta). At the sublimation temperature, DG = 0, and so you can solve for T.

Make sure you express all terms in either J or kJ.

Answer 2

Just going by units to get Kelvin I would divide 62000 by 145. That gives about 400 K or 130 deg C, which seems about right. It doesn't take a lot of heat to make iodine sublime if you have seen the demo.