Can something that dissolves in water be hydrophobic?

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In summary, the conversation discusses the possibility of driving hydrophobic H2CO3 molecules to the surface of a liquid, as well as methods of salting out and changing the properties of molecules. However, it is unlikely that the CO2 case would work as the substance is typically distributed uniformly in solution. The use of salt to increase ionic strength may have a similar effect, but it is not possible to change the properties of a molecule without altering the molecule itself.
  • #1
rwooduk
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This may be a really stupid question, but I'm going to go ahead anyway.

Say I have CO2 and dissolve it in water to give H2CO3, are / could the H2CO3 molecules be hydrophobic?

To put this in context I want to somehow drive the H2CO3 molecules to the surface of the liquid. Does this make sense? Would this be possible?
 
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rwooduk said:
Does this make sense?

Not much. Whatever is dissolved is more or less uniformly distributed. Sure, there can be a concentration gradient, but that happens when there is no mixing and you either add or remove the substance on the solution surface. Otherwise it is unlikely.
 
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Borek said:
Not much. Whatever is dissolved is more or less uniformly distributed. Sure, there can be a concentration gradient, but that happens when there is no mixing and you either add or remove the substance on the solution surface. Otherwise it is unlikely.

That's very helpful, thanks!

To be more specific, I am reading a paper that uses salt to increase the ionic strength of a liquid, so that hydrophobic organic pollutants in the liquid are driven to the surface. Please could you lend some insight into how this differs from the CO2 case above?

Again, apologies if this makes little sense.
 
  • #5
Borek said:
https://en.wikipedia.org/wiki/Salting_out

Interesting. I see it has a similar method.

Do you know of any methods to make a particular molecule hydrophobic, so that it could be "salted out"?
 
  • #6
I general you can't change properties of a molecule* without changing the molecule itself.

*At least for small, simple ones. when it comes to large ones like proteins things get more complicated, as a lot depends on what you mean by "changing" the molecule.
 
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Borek said:
I general you can't change properties of a molecule* without changing the molecule itself.

*At least for small, simple ones. when it comes to large ones like proteins things get more complicated, as a lot depends on what you mean by "changing" the molecule.

Hm, that's unfortunate, but okay you have been very helpful, thanks again!
 

1. What does it mean for something to be hydrophobic?

Hydrophobic substances are ones that repel or do not mix well with water. This is because they have a nonpolar molecular structure, which does not interact well with the polar structure of water molecules.

2. Can something that dissolves in water still be considered hydrophobic?

Yes, it is possible for a substance to be both hydrophobic and dissolve in water. This is because the substance may have both polar and nonpolar parts, with the polar part interacting with water molecules and the nonpolar part repelling them.

3. How can a substance dissolve in water if it is hydrophobic?

A substance can dissolve in water if it has a polar part that can interact with water molecules. This allows the substance to be surrounded by water molecules and become dispersed in the solution, even if the overall substance is hydrophobic.

4. Are there any benefits to having hydrophobic substances dissolve in water?

Yes, there are several benefits to this phenomenon. One example is the use of detergents, which have both hydrophobic and hydrophilic parts, to help remove dirt and oils from surfaces. Additionally, hydrophobic compounds can be used in drug delivery systems to target specific tissues in the body.

5. How can you determine if a substance is hydrophobic?

There are several ways to determine if a substance is hydrophobic. One way is to observe if it forms a separate layer when mixed with water, indicating that it is not mixing well with the water. Another method is to perform a contact angle test, where a droplet of water is placed on the substance and the angle at which it sits on the surface is measured. A higher contact angle indicates a more hydrophobic substance.

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