Today is more of a lesson rather than working through a problem. Regardless this lesson will help you greatly with your exam preparation.
As I prepared for my second year thermodynamics exam I ran into a number of formulas for work. Its open book, who cares, simple, I'll figure it out if I need them in the exam. However, there are a lot of assumptions associated with each formula that are very specific to their application. We all know that reading and acquiring knowledge simply does not happen in a time crunched exam.
The video below is a thorough explanation of the different work formulas and when to utilize them.
A few definitions are your takeaways today:
Also note that most examiners and teachers will take it for granted that you know what throttling is and that you know it is an adiabatic process. Throttling is a means of choking flow and creating a pressure drop across a valve or some sort of orifice (giggity). Thus the assumption of adiabatic conditions will not be mentioned in the question, you must recognize it and apply the formula mentioned in the video.
As always feel free to ask for further clarification below and send any requests to myemail.
Mike Grossman, P. Eng.