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

Dec 5, 2016

$n = \frac{P V}{R T}$; a mass of approx. $4 \cdot g$ of fluorine obtains.

#### Explanation:

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

$= \frac{\left(375 \cdot \text{Torr")/(760*"Torr} \cdot a t {m}^{-} 1\right) \times 5.12 \cdot L}{0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1 \times 298.9 \cdot K}$

$\cong$ $0.10 \cdot m o l$

Now fluorine gas, ${F}_{2}$, has a mass of $38.00 \cdot g \cdot m o {l}^{-} 1$, 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.