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

1 Answer
Feb 2, 2016

Answer:

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.