Exercise 9 | Chemical Thermodynamics

Calculate ΔH0vap [Br2] given that the vapor pressure of bromine is 133 Torr at 293K and 48.1 Torr at 273K.

Clapeyron-Clausius equation :

ln P2P1 = H0rxnR x 1T1 - 1T2

ΔH0rxn = R ln P2P1 x T1T2T2 - T1

 

Situation 1: P1 = 133 Torr and T1 = 293K

Situation 2: P2 = 48.1 Torr and T2 = 273K


ΔH0vap = 8.314 x ln 48.1133 x 273 × 293- 20

ΔH0vap = 33.8 kJ.mol-1