Can I use a docking station to connect my iMac 24" to a second monitor?

Yes, I have done it with my OWC dock, but you cannot connect more than one external monitor to the system. i.e., you cannot connect one to the thunderbolt port on the iMac and another to the port on the dock.

that would depend on the docking station in question

but you can connect the thunderbolt ports directly by cable to monitors