# molarity of HCl

Thomas Hettmann hettmann at physik.mu-luebeck.de
Mon Oct 20 11:35:50 EST 1997

```RUTH MCMAHON wrote:
>
> In my lab we cannot agree on the molarity of the following solution.
> On a bottle of concentrated HCl is the following information,
> mw = 36.36
> 1.19kg = 1L
> 37%.
> There are conflicting views of
> 10.15M
> 11.2M
> 12.01M.
> Could someone please explain the correct way of calculating this.
> Thankyou.
>
> Ruth.

Let's start with the 37%. If nothing else is specified, that means
weight per weight, i.e. 370 g of HCl per 1 kg of solution.
->  370 g/kg
The density is 1.19 kg/L
->  370 g/kg * 1.19 kg/L = 440.3 g/L
(that is 440.3 grams of HCl per litre of solution)
The molecular mass is 36.36 g/mol, well, on the bottle in our lab it is
36.46 g/mol.
-> (440.3 g/L) : (36.46 g/mol) = 12.08 mol/L

Hope that helps,
Thomas

PS: Why don't you just look it up? Oddly, I found a value of 12.5 mol/L
in my table.
--
Thomas Hettmann - Institut fuer Biochemie
Medizinische Universitaet zu Luebeck
Ratzeburger Allee 160
23538 Luebeck
Fax: +49-451-500-4068
E-Mail: hettmann at physik.mu-luebeck.de

```