What is the medium size of a Hydrochloric acid molecule?

[JorgeM]

I was just thinking on the fact that there are some comercial gas masks . These ones have a filter, that doesn´´´'t let the Hydrochloric acid gas molecules to go into the mask. This is the way it basically works, isn't it? So this filther has some little holes that are smaller than these molecules.
But I do not really know what is this medium size in fact. I have been looking for some information but I have't found that yet. Do you know where Can I find this information?
I have tried to look up this on the web but there is a lot of other physical info, that doesn't answer my question.
Or if you know in which parameter Do I have to look up the answer.
I would be grateful if you let me know.
Thanks a lot for your time

JorgeM

 

[Borek]

It is not like these filters work, they do absorb the HCl, but not by filtering due to size. That works for much larger things only.

Molecule size is not something that is well defined, molecules don't end abruptly like a macroscopic object (say: a pencil) does, it is more like their electron cloud gets less and less dense and at some arbitrary point we say "it already ended". That means you will not find an exact answer.

Wikipedia gives the bond length between H and Cl. Molecule will be less than twice longer.

And don't get me started on the differences between hydrogen chloride and hydrochloric acid, these are often mixed up. Yes, they are strongly related, no, they are in too many ways different to treat them as the same thing.

 

[HAYAO]

Most of the filters used in gas masks are zeolites and activated carbon. The working principle is that the substance coming into the filter is either absorbed, adsorbed, or reacted. The "little holes" you are talking about are for little particulates that are physically large enough that they can be filtered.

But molecules are not particulates, and they are definitely physically smaller than few nanometers, if not, even smaller. At such scales, "physical size", as Borek mentioned, is not quite discrete. Electrons that are moving around the atomic nuclei will have a probability density (distribution of the likelihood that the electrons will be at certain position around the nuclei) and they extend outward. Imagine an bell curve (Gaussian distribution):

Where does the curve start and where does it it? It's hard to say, isn't it? The curve is zero only at minus infinity or positive infinity. Basically, electrons also behave similar to this. It has a distribution without clear boundary of where it ends.

Most researchers, when really necessary, may use the van der Waals volume to refer to molecular sizes. They are definitely far from perfect in predicting behavior attributed to their molecular sizes (since it's not just about the size but also about interactions).

 

[naresh123]

Yes, Molecular size is not mentioned perfectly on any sources,