How to determine the volume of a substance produced when only given the equation at STP?
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.