Question

A `4.500*mol` quantity of stuff has a mass of `232.0*g`. What is the molar mass of the stuff?

Answer 1

Divide the mass by the given molar amount.

Explanation:

`"Mass"/"Molar quantity"` `=` `"Molecular mass"`

You have been quoted the mass, `232.00` `g`, and also quoted the molar quantity, `4.500` `mol`.

So `"232.00 g"/"4.500 moles"` `=` `51.56` `g` `mol^-1` as required. By putting the dimensions in the answer, automatically I got the right units for the answer as well, `g` `mol^-1`. I also used the conversion `"1 lb"` `=` `454` `g`.

So what is a mole? It is simply a NUMBER of molecules, like a dozen, or a gross, or a 1000. If there are 1 mole of stuff there `6.022xx10^23` individual items of that stuff. This is something fundamental that I would try to get my head around.

The mole is the link between grams and kilograms (and even pounds), what we measure in a lab on a benchtop, and the micro world of atoms and molecules, what we conceive of and theorize. So if you measure out a mass of given substance, and you know the molar mass of that substance, you know precisely the number of particles, of atoms and molecules, that constitute that mass.