Chemistry
Chemistry
Problem
Solid iodine melts at 113 °C and boils at 184 °C under 1 atm pressure. The enthalpy of fusion at 113 °C is 15.5 kJ mol⁻¹, and the enthalpy of vaporization at 184 °C is 41.6 kJ mol⁻¹. a. Determine the molar enthalpy of sublimation of iodine at 1 atm, assuming that the temperature dependence of ΔH is negligible over the range considered. Show your calculation. b. Using your result from part (a), describe the physical significance of the enthalpy of sublimation in the context of the relative strengths of intermolecular forces in the solid and gaseous phases of iodine.Intuitive explanation
The key to phase changes is understanding that energy goes into breaking bonds between molecules, not raising temperature. Here, you're tracking how much heat is needed to push iodine through two distinct transitions: melting (solid → liquid) and vaporization (liquid → gas). Each transition has its own enthalpy cost at its specific temperature, so you'll use and directly rather than calculating temperature changes.
Intuitive explanation
The key to phase changes is understanding that energy goes into breaking bonds between molecules, not raising temperature. Here, you're tracking how much heat is needed to push iodine through two distinct transitions: melting (solid → liquid) and vaporization (liquid → gas). Each transition has its own enthalpy cost at its specific temperature, so you'll use and directly rather than calculating temperature changes.