Use these data to calculate the molar mass of an unknown diatomic gas

Initial mass of empty flask and top $=86\mathrm{.}8234$ g

Final mass of flask, top and gas $=87\mathrm{.}7431$ g

Flask Volume$=1026\mathrm{.}8$ mL

Barometric Pressure$=0\mathrm{.}9758$ atm

Temperature$=99\mathrm{.}00\backslash$deg C

What is the identity of the gas?