F2 means that there are two flourine's usually a gas is a diatomic molecule.
Since a fluorine molecule has an atomic mass of 18.998 that molar mass of F2 would be 18.9998 *2 = 37.996 except in molar mass the units change so instead of being g/mol it would just be grams.
so 37.996 grams
hope this helps!
(:
