How can I put a chemical stoichiometry equation with units into W|A?

I have an equation like the following:
chemeq.gif

And I want to have it solved by Wolfram|Alpha. I know the engine can handle units and chemistry, but I can’t make it recognize this input, even if I enter it as TeX. How would you enter this so that the computer can read it?

That’s a rather large input for Wolfram|Alpha. I also am not sure how well it would handle unknown units like this.

For a calculation like this, I would use Mathematica online.
In Mathematica, new units can be respresented with the IndependantUnit expression: IndependentUnit—Wolfram Documentation