link web application to a specific process

Try giving it its own AppPool.  I think that will break it out as a separate process.

ok, but how would it be identified?  at the moment, all web apps have their own process, but the same name (w3wp.exe).

Yes, it will be difficult to identify a particular process, but you can use Task Manager to see the Process ID (go to View -> Select Columns) and leverage that.  

SysInternals also has a variety of tools (including Process Monitor and Process Explorer) that can tell you what applications are associated with what processes.

I'm sorry, but I understand how to get process id from task manager.  I just don't understand how to link it to the specific web application. How can I do that?

Well, you can't.  The process IDs are assigned as processes start.  What ID a process gets depends on the order of all processes starting.

so there's no way to determine which of the apps is using the greatest amount of cpu?  How do web admins know which apps are eating up their server resources, then?  How do they know when to shut down an errant web app?

now i understand.  that worked perfectly to identify the app pool.  thanks.

Happy to help and good luck with your troubleshooting!