Alright sorry all, this is how I thought to do it.
First we need to find the energy of the phase change, where q=m*Change in HVAP.
So: (100g/78g/mol)=1.28mol*30.8kJ/mol=39.42kJ. But the problem is, the equation calls for mass, but the constant in in moles/kJ. Here, I converted to moles.
Then: Q=M*C*Delta T so Q=100g*1.72j/g*C *55 degrees Celsius. so Q=9460J, or 9.46 kJ.
Using Hess's Law we can add those two numbers, yielding 48.9 kJ of energy.
That is how I thought to to it, but how we did it in class dealt with proportions. Does anyone see any problems in my work?
Thanks for looking!