What is the mass in grams of 5.50 moles of Copper, Cu?

349.503 g

https://www.convertunits.com/from/moles+Copper/to/grams

here is a link, you can convert moles of copper to grams here

a boiling water reactor does not boil the water. a pressurized water reactor boils the water faster. a pressurized water reactor is heated directly by the core. a pressurized water reactor does not use fission.

tracks, burrows, eggshells, nests, tooth marks, or gastroliths