# Question e7787

Oct 17, 2015

I'm not sure what "shelf molarity" means.

#### Explanation:

First thing's first, the molarity of a concentrated hydrochloric acid solution does not come near $\text{36.5 M}$.

What you have there is actually percent concentration by mass. The most concentrated hydrochloric acid solutions available are about 37-38% "m/m". At concentrations that exceed 40%"m/m" hydrochloric acid is actually fuming.

The molarity of a 36.5%"m/m"# hydrochloric acid solution is approximately $\text{12 M}$, so that value is actually correct.

You can calculate this value by using the hydrochloric acid solution's density

http://www.handymath.com/cgi-bin/hcltble3.cgi?submit=Entry

What you do is take a $\text{1-L}$ sample of the stock solution, then use its density and percent concentration by mass to figure out how much hydrochloric acid it contains.

Now, I'm not entirely sure what shelf molarity means. The closest term I'm familiar with is shelf life, which basically gives you an idea about a compound's stability, i.e. how much time you can expect to pass until you see any chemical changes occuring.

As far as I know, hydrochloric acid does not have a shelf life, provided that you store it properly - this is expecially true for concentrated hydrochloric acid solutions, which tend to evaporate at significant rates.