A weighed quantity of a gas is collected over water at ${25}^{\circ }\mathrm{C}$ and $742 \mathrm{mm} \mathrm{Hg}\text{.}$ The molar mass a of the is to be determined at standard temperature and pressure. If the vapor pressure of water is ignored during the calculation, what is the effect on the calculated pressure and calculated molar mass of the gas?

Pressure                            Molar mass

law                                     law

Pressure                            Molar mass

law                                     high

Pressure                            Molar mass

high                                    law    

Pressure                            Molar mass

high                                  high