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

Feb 2, 2016

Divide the mass by the given molar amount.

Explanation:

$\text{Mass"/"Molar quantity}$ $=$ $\text{Molecular mass}$

You have been quoted the mass, $232.00$ $g$, and also quoted the molar quantity, $4.500$ $m o l$.

So $\text{232.00 g"/"4.500 moles}$ $=$ $51.56$ $g$ $m o {l}^{-} 1$ as required. By putting the dimensions in the answer, automatically I got the right units for the answer as well, $g$ $m o {l}^{-} 1$. I also used the conversion $\text{1 lb}$ $=$ $454$ $g$.

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 $6.022 \times {10}^{23}$ 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.