If the atmospheric pressure is not corrected for vapor pressure of water, what effect will this have on number of moles of oxygen calculated? Use numbers from your experiment and determine the percent deviation caused by this omission. Is this a significant error?

this is a lab report question after a lab where and unknown KClO3 was mixed will Fe2O3 and heated to break it down. The oxygen created from this reaction forces water out of an erlenmeyer and into a beaker. The oxygen is calculated by the amount of water displaced.