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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Restless_Fillmore on June 16, 2021, 10:20:10 PM

Title: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Restless_Fillmore on June 16, 2021, 10:20:10 PM
I'm not a student, but these seem to be undergraduate-level questions...

Some analytical laboratory methods report "dissolved hydrogen" (for an aqueous matrix).  Why is "dissolved hydrogen" not just related to a pH measurement of the H+ ion?  I know that "dissolved hydrogen" is reporting the H2 molecules, but why would that be considered "dissolved" and not just a mixture, as it's not dissociated?


 Is it actually a mixture but is called dissolved by convention, or is it actually somehow truly "dissolved"?


Thank you.
Title: Re: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Borek on June 17, 2021, 02:47:57 AM
Solution is a mixture, to some extent these terms are used interchangeably. It has nothing to do with the dissociation.

Why is "dissolved hydrogen" not just related to a pH measurement of the H+ ion?

Because H+ and H2 are two completely different things, not related to each other in a simple, non trivial way.
Title: Re: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Orcio_87 on June 17, 2021, 08:07:12 AM
Quote
Is it actually a mixture but is called dissolved by convention, or is it actually somehow truly "dissolved"?
It is a solution, not a mixture or colloid, as H2 particles are small enough to fulfill solution definition.
Title: Re: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Restless_Fillmore on June 17, 2021, 11:56:44 AM
Quote
Is it actually a mixture but is called dissolved by convention, or is it actually somehow truly "dissolved"?
It is a solution, not a mixture or colloid, as H2 particles are small enough to fulfill solution definition.

Thanks.  What is the source of "official" definitions for the field of chemistry?  Would it be the Oxford Dictionary of Chemistry, or something else?
Title: Re: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Borek on June 17, 2021, 12:41:17 PM
What is the source of "official" definitions for the field of chemistry?

IUPAC

https://goldbook.iupac.org/terms/view/S05746#:~:text=Also%20contains%20definition%20of%3A%20solvent,substances%2C%20which%20are%20called%20solutes.
Title: Re: Why is it "dissolved" hydrogen instead of being considered a mixture?
Post by: Orcio_87 on June 17, 2021, 12:49:25 PM
Quote
What is the source of "official" definitions for the field of chemistry?  Would it be the Oxford Dictionary of Chemistry, or something else?
No, only IUPAC is truly official source of the definitions.

ISO standards are official source of the laboratory procedures.