43. Solution to Chemistry Problem

7. For substance A, the following are given: heat of vaporization, heat of sublimation, densities of the solid and liquid phases dsolid, dliq at the triple point temperature Ttr.t. Based on these data: 1) calculate the boiling point of substance A using the Truton equation; 2) write the equation IgPliq = a/Tb (a and b are constants) for the liquid ↔ vapor equilibrium; 3) use the resulting equation to calculate the saturated vapor pressure of A at the triple point; 4) write the equation lg Psolid = a’/Tb’ for the solid phase ↔ vapor equilibrium; 5) calculate dP/dT for the solid phase ↔ liquid equilibrium; 6) plot a graph of the equilibrium pressure versus the phase transition temperature for three phase states in the pressure range from 0 to 1.013* 105 Pa. In this pressure range, the dependence of pressure on temperature for the equilibrium solid phase ↔ liquid phase is expressed by a straight line, i.e. dP/dT = const.

N Substance A T, K Heat of evaporation
10-4,
J/mol Heat of sublimation
10-4,
J/mol d¬solid*10-3, kg/m3 d¬liquid*10-3, kg/m3
7 KF 1159.1 18.04 20.68 2.43 1.914