Question

What is the mass of 500 molecules of `"NaCl"`?

Answer 1

There is no such thing as an ionic molecule, so I will instead calculate for `"500 formula units"`...

`"500 equiv. NaCl" xx ("1 mol")/(6.0221413 xx 10^(23) "things")`

`= 8.303 xx 10^(-22) "mols NaCl"`

(what is this `6.0221413 xx 10^(23)` number called?)

And each `"mol"` has a characteristic molar mass of `22.989 + 35.453 = "58.442 g"`, using the periodic table for `"Na"` and `"Cl"` (what are their names?).

As a result, the mass is:

`8.303 xx 10^(-22) cancel"mols NaCl" xx ("58.442 g")/(cancel"1 mol NaCl")`

`=` `ulcolor(blue)(4.852 xx 10^(-20) "g")`

Now, this number is absurdly small, but that should make sense, as we only have `500` particles, each a few nanometers in diameter, much, much less than a handful of salt formula units.