1

I'm reading Unit operations of Chemical Engineering, 5th edition by Warren McCabe.

They defined the "molar density $\rho_{M}$" as $\ce{\rho_{M}=\frac{n}{V}}$. The parameters $n$ and $V$ are the number of moles and volume as usual (they are indicated in the summary table of all the symbols at the end of the chapter). To my understanding, $\rho_{M}$ indicates how many moles of a molecule are there in a volume unit and its unit should be something like $\ce{mol/m^3}$ or $\ce{mol/cm^3}$. The definition of <span class=$\rho_{M}$" />

However, the unit of $\rho_{M}$ in that table is $\ce{kg\cdot mol/m^3}$. Why is there the presence of mass? The symbols with explanation at the end of the chapter

kamikaze
  • 57
  • 2
  • 4
    kg mol is the way some engineering texts refer to kmol (1000 mol). g mol is the same as mol. lb mol is useful if you're converting from mol to lb, for example the molar mass of water is 18 g/mol or 18 lb/lbmol. It is defintely confusing in a way since you can read "kg times mol", which is nonsense, though it is less confusing if you write it altogether: kgmol instead of kg mol. – Vinícius Godim Feb 09 '23 at 15:13
  • :) Thanks for your help. Now it makes a lot of sense. It was really confusing – kamikaze Feb 09 '23 at 15:17

0 Answers0