Liquid sodium can be used as a heat transfer fluid. It's vapor pressure is 40.0 torr at 633 degrees C and 400.0 torr at 823 degrees C. Calculate its heat of vaporization.
a) 43.4 kJ/mol
b) 52.5 kJ/mol
c) 70.6 kJ/mol
d) 1.00 x 10^2 kJ/mol
e) none of the above