[cemocles]

The problem:
Calculate the work done in joules when 1.0 mole of water vaporizes at 1.0 atm and 100 degree Celcius.  Assume that the volume of liquid water is negligible compared with that of steam at 100 deg Celcius, and ideal gas behavior.

I have no idea which equations to use, since there are so many dealing with thermodynamics and ideal gas situations.  Plus I don't understand what the second sentence specifically means.  Can someone please show me the solution step by step?

Thank you in advance.

[Yggdrasil]

Try w = P?V

[tamim83]

Use PV=nRT to calculate the volume of the water vapor.  Then use w=PdV to calculate the amount of work done.  A shortcut would be to plug the ideal gas law equation into the work equation. 

[cemocles]

Thank you all for the help, I've solved the problem!