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"?