Question

would the calculated molar volume be larger, smaller or unchanged.

a. the partial pressure of water was not taken into account

Answer 1

Usually when one does this experiment a volume of gas is collected over water and the volume is measured, then calculated to STP.

(P1V1/T1) = (P2V2/T2)

So V2 = (P1V1YT2/P1T1)
but P1 is the measured pressure of the wet gas. That is corrected to pressure of the dry gas by subtracting vapor pressure H2O, like this
V2 = (P1-H2O)V1/(P1T1)
If vapor pressure of H2O is not taken into account then P1 is used and not P1-vapor pressure H2O. That means you are using too large a number. How will that affect V2?