How to bake baking soda to produce sodium carbonate? I'd like to make sodium carbonate for ramen noodles. The instructions on the web however vary greatly. One source says to bake baking soda at 350 degrees for 2-5 hours. Others say 250 degrees for an hour. Another says just 200 degrees for an hour.

Does the temperature even matter at all? 

How about if I use a higher temperature like 450 degrees? This would be preferable for me as I only need a small amount and I can probably bake it at the same time I'm baking bread.
The temperature needs to be high enough, that's all. 450°F should work fine.  (2-5 hours is a little silly, since the reaction is pretty quick once the baking soda itself is up to temperature.)

If you want to check that everything's gone okay, you can weigh the powder before and after. If it's converted properly, its mass should decrease to 63% (EDIT: fixed miscalculation, Matthias' number is the correct one) of the original. (Possibly a little further if there was some moisture in it.)