posted by Madison on .
From data below, calculate the total heat (J) needed to convert 0.757 mol of gaseous ethanol (C2H6O) at 151°C and 1 atm to liquid ethanol at 25.0°C and 1 atm.
Boiling point at 1 atm 78.5°C
cgas 1.43 J/g·°C
cliquid 2.45 J/g·°C
ΔH°vap 40.5 kJ/mol
It's easier to work these problems in steps. There are two types of steps you use.
For phase changes (solid to liquid or liquid to gas OR the reverse) you use
q = mass x delta H.
delta H is heat fusion for solid to liquid or reverse.
delta H is heat vaporization for liquid to gas or reverse.
The second type is for heating/cooling within a phase; i.e., heating a liquid from 20 C to 100 C or cooling a liquid from 100 c to 20 C.