If the water temperature at the gas collection port is assumed to be 25 degrees celsius but it is actually 35, will your calculated molar mass be too high or too small

Question

If the water temperature at the gas collection port is assumed to be 25 degrees celsius but it is actually 35, will your calculated molar mass be too high or too small

Answer 1

Since you will be using the vapor pressure of water at the "temperature" where the gas is collected, the pressure you will use will be lower than the actual pressure (pressure at 25º is less than that at 35º). This value will be subtracted from measured pressure of the collected gas resulting is a pressure of collected gas that is greater than actual. From PV = nRT you will be solving for n, but the pressure (P) you use will be too high, so moles calculated will be too high. Since molar mass = mass/moles, the calculated molar mass will be too low.