Oxygen gas and hydrogen gas are used to synthesize dihydrogen monoxide. A lab group utilizes 1.00 liters of oxygen and 1.01 liters of hydrogen to create 0.75 grams of product. How many milliliters of product should the group have expected to get? What will the [H+] concentration be for the product? What was the group's percent error in this lab?

2H2+O2>>2H2O

They should have gotten 1.01liters of water vapor, or 1/22.4 * 18 grams.

as the vapor condenses, and cools to 25C, the H+ concen will be 1*10^-7 moles/liter

Milliliters of product? One has to have the temp and pressure.