Question

What mass of fluorine gas generates a pressure of `375*"Torr"` when confined to a `5.12*L` volume at `298.9*K`?

Answer 1

`n=(PV)/(RT)`; a mass of approx. `4*g` of fluorine obtains.

Explanation:

`n`, i.e. number of moles of gas, is given by the calculation:

`=((375*"Torr")/(760*"Torr"*atm^-1)xx5.12*L)/(0.0821*L*atm*K^-1*mol^-1xx298.9*K)`

`~=` `0.10*mol`

Now fluorine gas, `F_2`, has a mass of `38.00*g*mol^-1`, and thus a mass of `38.00*g*mol^-1xx0.10*mol=??g`.

Note that most elemental gases are DIATOMIC: dioxygen, dinitrogen, difluorine, dichlorine etc. The exceptions to this rule are the Noble Gases, which do not normally form compounds, but do habitually occur in gas problems on exams. This simply must be known.