Thanks for the reply. I didn't think MathJax supported it but was wondering how to get it to work without.
The link you gave me returned to this page., but i dug through some old papers from the 2.x days when I added chemarrows to WeBWorK, because I don't think they were in the version I was using.
From what I recall getting the package to load involves changes to hardcopyPreamble.tex and Constants.pm (maybe others...)
I haven't checked where the code leads Constants.pm to the texlive additions, but I Think all items are in (in UBUNTU 16.04LTS) /usr/share/texlive/texmf-dist/tex/latex/.
If You can offer any advice as to how to get this running I would appreciate the help.