phase change energetics

Question

The following information is given for mercury, Hg, at 1 atm:

boiling point = 357 °C	Hvap(357 °C) = 59.3 kJ/mol
melting point = -38.9 °C	Hfus(-38.9 °C) = 2.33 kJ/mol
specific heat liquid = 0.139 J/g°C

At a pressure of 1 atm, what is H in kJ for the process of condensing a 26.3 g sample of gaseous mercury at its normal boiling point of 357 °C.

Answer BLANK kJ

Answer 1

Condensing is the opposite of vaporization and so you can use ∆Hvap but you must change the sign from + to - and you must then change 26.3 g Hg to moles of Hg.

q = moles x ∆Hvap in kJ/mole = kJ of heat = ∆H