Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Very quick question on notation, M vs. M/L

  1. Sep 12, 2017 #1
  2. jcsd
  3. Sep 12, 2017 #2


    User Avatar

    Staff: Mentor

    M typically stands for mol/L. In this case M is mole per liter, mM is millimole per liter.

    I don't remember ever seeing M used to denote number of moles.
  4. Sep 12, 2017 #3
    Thanks Borek. I assumed this was the case but the high concentrations had me confused. i.e. I have been using 0.470g of phenol to make 10^-4 mol/L phenol stock solution = 0.1mMol/L.

    From the graph above they are using up to 100 mMol/L.

    If I calculate for 60mMol/L then I need 282g of phenol, which seems rather a lot.

    But anyway, thank you very much for clearing this up!
  5. Sep 12, 2017 #4


    User Avatar
    Science Advisor
    2017 Award

    The molecular weight of phenol is 94.1 g/mol. For a 60 mM solution:
    ##60\text{ mM} = \frac{60 \text{ mmol}}{\text{L}} * \frac{1 \text{ mol}}{10^3\text{ mmol}} *\frac{94.1\text{ g}}{\text{mol}} = 5.65 \text{ g/L}##

    Are you sure your calculation is correct?
  6. Sep 13, 2017 #5
    No I'm not. Thanks very much for that, I'm going to have to revisit my basic chemistry, the more focused I get in my research the more the basics are leaving me, I got a first class degree in physics and can't remember anything !!! Will recalculate everything this morning, thanks again!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted