Impossible to centrifuge salt out of water?

[wasteofo2]

I've been told (by my high school chemistry teacher, which obviously means it isn't necessarily true), that when salt dissolves in water, that you cannot centrifuge it out.

I understand that you can't centrifuge it out like you would sugar, or something that doesn't ionize, but it seems to me that you should be able to centrifuge it out.

Water can only accept a concentration of so many salt ions per so many water molecules, and once that acceptable concentration is exceeded, salt will precipitate out of solution, correct?

Furthermore, when salts dissolve in water, and the ions dissociate, the positive ions will tend to stick near the - end of water, and the negative ions will be attracted to the positive end of water. So, if you're dealing with an unsaturated solution, you have some water molecules that essentially have ions loosely bonded to them, making them heavier.

In that the water molecules that have ions attracted to them are heavier, it seems that if you centrifuge water, these molecules will go to the bottom of the centrifuge tube.

If you were to use enough force, it should seem that you'd get enough of the water with ions attracted to it to go to the bottom that you might actually surpass the molarity of ions that water can take, and that some salt would actually previpitate out.

Even if you couldn't get the proper ratio of ions to water molecules for salt to precipitate out, it seems that the ionic sides of the water should be sent furthest down, since the ions of any salt are heavier than water's components.

Is my logic correct?

 

[scrappychic]

That's a good point. I am curious to know the answer, too.

 

[ravenprp]

Your logic is partially correct, but there are some important factors to consider when trying to centrifuge salt out of water. First, let's define what it means for salt to be "centrifuged out" of water. This would mean that the salt is separated from the water and forms a solid layer at the bottom of the centrifuge tube, while the water remains at the top. However, as you mentioned, salt ions are attracted to the positive and negative ends of water molecules, so they will not necessarily form a solid layer at the bottom.

Additionally, the force of centrifugation may not be strong enough to overcome the attractive forces between water molecules and salt ions. This means that even if the salt ions do move to the bottom of the tube, they may still be dispersed throughout the water instead of forming a solid layer.

Furthermore, as you mentioned, the concentration of salt ions in water can only reach a certain point before the solution becomes saturated and no more salt can dissolve. This means that even if the centrifugation process does separate some salt from the water, it may not be enough to significantly reduce the overall concentration of salt in the solution.

In summary, while it is possible to separate some salt from water using centrifugation, it may not be a very effective method for completely removing salt from a solution. Other techniques, such as evaporation or filtration, may be more suitable for this purpose.