# Elemental sulfur occurs as octatomie molecules, S_8. What mass of fluorine gas is needed to react completely with 28.6 g of sulfur to form sulfar hexafluoride?

Sep 23, 2016

Approx. $100 \cdot g$.

#### Explanation:

We need (i) a stoichiometric equation:

$S \left(s\right) + 3 {F}_{2} \left(g\right) \rightarrow S {F}_{6} \left(g\right)$.

And (ii) the molar equivalence of sulfur and fluorine $=$

$\frac{28.6 \cdot g}{32.06 \cdot g \cdot m o {l}^{-} 1}$ $=$ $0.892 \cdot m o l$.

And thus $0.892 \times 3 \times 38.00 \cdot g \cdot m o {l}^{-} 1$ $\cong$ $100 \cdot g$ fluorine gas are required.

Just a note on the molecularity of sulfur, of course I could have treated it as ${S}_{8}$ as you did. The arithmetic is a bit easier if I give the equation as written above: 3 equiv of fluorine gas react with 1 equiv of sulfur. Note that fluorine, like all the other elemental gases (SAVE FOR THE NOBLE GASES), is binuclear, i.e. a diatomic molecule.