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

Aug 4, 2017

There is no such thing as an ionic molecule, so I will instead calculate for $\text{500 formula units}$...

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

$= 8.303 \times {10}^{- 22} \text{mols NaCl}$

(what is this $6.0221413 \times {10}^{23}$ number called?)

And each $\text{mol}$ has a characteristic molar mass of $22.989 + 35.453 = \text{58.442 g}$, using the periodic table for $\text{Na}$ and $\text{Cl}$ (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")

$=$ $\underline{\textcolor{b l u e}{4.852 \times {10}^{- 20} \text{g}}}$

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.