Solve Isentropic Expansion: Mass 0.45 kg, 10 bar, 622°C to 331°C, 85 kJ Work

[beeniemac]

Homework Statement

A mass of 0.45 kg of a perfect gas with a ratio of specific heats of 1.41 expands isentropically by means of a reversible non-flow process from an initial pressure of 10 bar and temperature 622oC to a temperature of 331 oC whilst generating 85 kJ of work. The specific heat at constant volume in J/kgK for the gas is?

Homework Equations

The Attempt at a Solution

I really have no idea where to start. I have attended all of my lectures and read all of the notes, but I just do no know where to come at this problem from..?

 

[Carid]

Why not start by reading this page
http://en.wikipedia.org/wiki/Heat_capacity_ratio