Question

How many moles of disulfur decafluoride are present in `1.55*10^22` molecules of this compound?

Answer 1

Approx. `0.025*mol`

Explanation:

There are `6.022xx10^23` `S_2F_10` units in one mole of the stuff by definition.

And thus `(1.55xx10^22" molecules")/(6.022xx10^23" molecules mol"^-1)` `~=` `0.025*mol`

`S_2F_10` is nasty stuff, though apparently it is quite odourless (this is a "good" property in a war gas, because some punter might get a lethal dose of it before he realizes he has been gassed; the substance has never been deployed in war).

Note that in this problem we could substitute any formula in the equation, and get the molar quantity.