Find the mass, in grams, of 5.00*10^23 molecules of f2

  31.55 g

Explanation:

- The mass number of Fluoride atom (F) = 18.99 g/mol, so mass number of         fluorine gas (F2) = 37.98 g/mol.

-  1 mole of (F2) [which has 37.98 g/mol] contains Avogadro’s number of molecules (6.02×10^23 molecules),

   so   1 mole of (F2) with 37.98 g/mol →  6.02×10^23 molecules.

- Using cross multiplication,  

                               37.98 g/mol of (F2)        →       6.02 ×10^23 molecules

                                                       ?              →        5.00 ×10^23 molecules

Hence the mass of 5.00×10^23 molecules of F2 = (37.98 × 5.00 × 10^23) / 6.02 ×10^23 = 31.55 g..