While editing The Curse of Judas I stumbled upon this conundrum. So I did a little research.
If you can substitute the word “while” then it is okay to use “whereas” as one word. If you cannot, then use “where as” as two words.
I stumbled upon a very interesting blog post while I was researching. If you want to learn more about the history of “whereas”, head over to the link below.
Happy writing my friends!