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

1. Sep 12, 2017

### rwooduk

2. Sep 12, 2017

### 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.

3. Sep 12, 2017

### rwooduk

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!

4. Sep 12, 2017

### Ygggdrasil

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?

5. Sep 13, 2017 at 3:45 AM

### rwooduk

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!