What is the molar mass of the solid?

A gas has a density of 8.0 g.L-1 at 2.81 atm and 300.0 K. a). What is the molar mass of the gas?

• A gas has a density of 8.0 g.L-1 at 2.81 atm and 300.0 K. a). What is the molar mass of the gas? b). What is the molecular formula of the gas if it contains only C, H and F? If the compound contains 1 carbon atom? I found the molar mass to be 70.08. How do i do part b?

• Answer:

  The key to it would be the atomic weights of carbon (12), hydrogen (1), and fluorine (19). Some combination of these should add up to 70. One possibility is C4H3F (because 48 + 3 + 19 = 70), but it seems a bit unlikely because all the carbons would have to be double-bonded... If the compound contains only one carbon atom, it could be CHF3 (12 + 1 + 57 = 70). This seems much more likely, because it would look just like methane, except with 3 of the hydrogens replaced by fluorines. This even makes me think you got the molar mass right, without my having to redo it!!