Final answer:
If the outside of flask A was wet during weighing, it would cause the measured molar volume of oxygen gas to be erroneously higher because the added mass from the water would make the gas appear to be more than it actually is.
Step-by-step explanation:
When you are performing an experiment to measure the molar volume of oxygen gas, the accuracy of your results relies on correct measurement practices, including the weighing of substances and apparatus. In step 14, if the outside of flask A was wet when you weighed it, this would add extra mass to your measurement, and as a result, the mass of the gas would appear greater than it actually is. Since molar volume is calculated based on the amount of gas produced, the added weight from the water would cause the calculated molar volume of oxygen to be higher than the actual volume. This is because you would be dividing the mass (which is erroneously high) by the molar mass of oxygen, ending up with a larger volume for one mole of gas than is correct.