Question

What is the mass of `4.49*10^25` particles of `HCl`?

Answer 1

`"Number of HCl particles"/"Number of HCl particles per mol"` `xx36.5*g*mol^-1` `=` `??`

Explanation:

It is a fact that `6.022xx10^23` individual `HCl` particles have a mass of `36.5` `g`. This is simply another way of saying that the molar mass of `HCl`, the mass of `"Avogadro's Number"` of `HCl` particles, is `36.5*g*mol^-1`.

So, all we have to do is divide the given number by Avogadro's number to get the number of moles, and then multiply this number by the molar mass:

`"Number of HCl particles"/"Number of HCl particles per mol"` `xx36.5*g*mol^-1` `=` `(4.49xx10^25)/(6.022xx10^23)` `xx` `36.5*g` `=` `??` `g`