Posted by Deborah on Saturday, June 12, 2010 at 2:20pm.
You must calculate the heat evolved in stages, then add all of the heats together to obtain the sum. Here is the way you go about it.
q1 = heat lost in moving the vapor from the starting point to the boiling point.
q1 = mass vapor x specific heat vapor x (Tfinal-Tinitial) where Tfinal will be the boiling point and Tinitial is where you start.
q2 = heat lost in condensing the vapor at the boiling point.
q2 = mass vapor at the boiling point x delta Hvaporization.
q3 heat lost in cooling the liquid vrom the boiling point to the melting (freezing) point.
q3 = mass liquid x specific heat liquid x (Tfinal-Tinitial) where Tfinal is the melting point and Tinitial is the boiling point.
q4 = heat lost is freezing the liquid.
q4 = mass liquid x heat fusion.
q5 = heat lost in moving the temperature from the freezing point to the final T.
q5 = mass solid x specific heat solid x (Tfinal - Tinitial) where Tfinal is the final T and Tinitial is the melting point.
qtotal = q1 + .....q5.
Watch the units. I note most of the specific heats are in J or kJ/mol but the mass is in grams.
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