Reef Chemistry Question of the Day 291: Supersaturation

Randy Holmes-Farley

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Reef Chemistry Question of the Day 291

Here's a thought experiment.

Suppose I take three vials of RO/DI water and add a pure single chemical to each (might be the same or different chemicals or amounts in each vial). They do not seem to dissolve completely with mixing at room temperature, so I heat them up and mix some more. In all cases, the water goes clear as all the solids dissolve.

I let them cool overnight, and get vials that look like the picture below. One is clear (A), one is a little cloudy (B), and one is very cloudy (C).

1685114254818.png


Which one or two of these solutions is the most likely to be supersaturated when the picture was taken?

Good luck!

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EeyoreIsMySpiritAnimal

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A.

Edit: I would say "C" but once there is precipitate, isn't the solution now stabilized at "saturation"?

That's why I chose "A", because nothing has precipitated out so the solution might still be supersaturated.
 
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Edgecrusher28

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Going to say A is super saturated to the point it does not all the solution to precipitate. Maybe by raising the temperature it allowed a higher saturation point and then by calling the solution it became super saturated, but literally just guessing. I suppose it make similar sense why water can become supercooled yet remain a liquid, or how with different temps and pressures water can exists in its triple phase.
 
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A.

Edit: I would say "C" but once there is precipitate, isn't the solution now stabilized at "saturation"?

That's why I chose "A", because nothing has precipitated out so the solution might still be supersaturated.
e.g. "From a thermodynamic point of view, a supersaturated solution will precipitate solid until it reaches an equilibrium state..."
 
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Randy Holmes-Farley

Randy Holmes-Farley

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I’m changing my answer to A.

Since A needed to be heated to dissolve, and did not precipitate out after being cooled, it is supersaturated.
 
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I’m changing my answer to A.

Since A needed to be heated to dissolve, and did not precipitate out after being cooled, it is supersaturated.
Copy cat ;)
 
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