How to determine the volume of a substance produced when only given the equation at STP? At standard temperature and pressure, what volume in $\pu{mL}$ of $\ce{H2O}$ is produced in the following reaction?
  $$\ce{2 KOH(l)  +  H3PO4(l)  -&gt;  K2HPO4(l)  + 2 H2O(l)}$$ 


Most questions I've found have more information than this so I'm confused as to how to do this problem.

I've tried multiplying $\pu{2 mol}$ of $\ce{H2O}$ by $\pu{22.4 L}$ and then converting it to $\pu{mL}$, but I've a feeling that isn't right.
I think you erred in multiplying 2 moles of water by 22.4 L. There are 55.5 moles of water per liter of water. Keeping this relationship in mind, use dimensional analysis to find the moles of water produced in your reaction. 

You're confusing the number 22.4 with the fact that 1 mol of gas at STP occupies approximately 22.4 L.