Question

Chlorofluocarbon was once used in air conditiones as the heat transfer liquid its normal boiling point is -30 degrees C and its enthalpy of vaporization is 16J/g. The gas and the liquid have specific heat capacities of 0.61 J/g8C and 0.97 J/g*C, respectively. How much thermal energy is evolved when 10.0 g CCL2F2 is cooled from 40 degrees celsius to -40 degrees celsius

Answer 1

I will save myself a lot of work and let you do most of it but here is how to go about it. First, identify any phase changes (solid to liquid or liquid to gas).
q at any phase change = mass x heat vaporization (if vapor to liquid or liquid to vapor) or heat fusion (if liquid to solid or solid to liquid).
Between phase changes it is
q = mass x specific heat in that phase x (Tfinal-Tinitial).
Then add all of the qs together for the total.