# Is it easier to mix a solution that is in the liquid or in the vapor phase?

In the article on dilution, Wikipedia has the following statement:

The same direct relationship applies to gases and vapors diluted in air for example. Although, thorough mixing of gases and vapors may not be as easily accomplished.

I was wondering if there is any supporting evidence for the second statement in the quote (or for the opposite statement). I would think that gases mix quickly, given how quickly gas expands into a vacuum (I am thinking of the classic picture of half a container filled with gas, and a divider that is removed). On the other hand, I don't know how effective mechanical mixers are for the gas phase. For the liquid phase, it is common to mix large volumes with a magnetic stir bar whose volume is comparatively small.

Is it easier to get a homogeneous mixture for a liquid phase than a gas phase? I am excluding immiscible liquids from the question because they will never become a homogeneous solution. To focus the question a bit, I am interested in the rate of mixing; to make it comparable, the mole ratios should be equal in the comparison of the liquid phase case and the gas phase case. Mixing could either be by diffusion, or sped up by a mixer appropriate for the system.

• It might refer to problems other than achieving homogeneity. See for instance en.wikipedia.org/wiki/Gas_blending Oct 24, 2020 at 20:34
• I think that's comparing pears and apples, and to the statement on wp, I say "balderdash". ;-)
– Karl
Oct 24, 2020 at 21:26
• The overriding factors are solubility and viscosity. Since, AFAIK, all gases are miscible, and have much lower viscosity than liquids (except perhaps He II), then it would be easier to get a uniform gas mixture with the same amount of work. That said, they might be talking about getting a uniform mixture in a specific situation, e.g. IC engine cylinder bore or burner nozzle. Oct 25, 2020 at 4:42