Okay, so we’re arguing over definitions now. Does the federal government have a basic duty to serve the nation? Yes. Has it been given a list of the powers available to it in order to fulfill that duty? Yes. Can those powers therefore also be described as duties? Who freakin’ cares.
Calling the Constitution a "list" is not just a semantic error, it's a factual one.
Can those powers therefore also be described as duties?
No they can't.
A power is something that you may use.
A duty is something you must perform.