1. The problem statement, all variables and given/known data An insulated piston-cylinder device contains 5 kg of water at 100oC with a quarter of the mass is vapor. The water is compressed reversibly to 900 kPa. Find the work done during this process. Let the ambient temperature to be 27oC. 2. Relevant equations I can use the energy balance equation 3. The attempt at a solution I am not sure how to continue and find the work of an irreversible process. What equation shall i take to find the work in a piston device?