Sciencemadness Discussion Board

Anhydrous ions

sternman318 - 21-5-2011 at 08:40

Is it possible to make a sample of dry ions? For example, a few grams of pure dry Mg2+, no water or other solvent . If so, what kind of behavior do they exhibit?

Sedit - 21-5-2011 at 08:46

I believe they are known as Ionic liquids and I remember some discussion on them a while back. They seem pretty interesting. I have always woundered how they would be for generating Alkali metals thru electrolysis since they are in essence just a liquid salt.

woelen - 21-5-2011 at 08:46

Anhydrous salts contain such "dry" ions. An example is NaCl, which consists of a lattice of Na(+) and Cl(-) ions. Anhydrous MgCl2 is another example, which contains of Mg(2+) and Cl(-) ions in a 1 : 2 ratio.

A macroscopic sample of pure Mg(2+) without counter ions is not possible. Even a tiny amount would have a tremendous charge.

So, ions without coordinated molecules of water (or more general: solvent) certainly are possible, but these always have counterions, such that the total charge of the solid is 0.

Random - 21-5-2011 at 14:43

I was once thinking about what would happen if somehow I would precipitate all ions except Na+ from solution. But then, I think it would immediately form NaOH because of water. If somehow pure ions would be isolated without solvent, they would make at least oxides from the air. But when they are formed in the very inert material like helium, what happens then?

This is just my theory, may be incorrect.

Then I read about free radicals, they can also be highly reactive ions. Maybe those are we are talking about, chlorine molecule (Cl2) for example forms it's two Cl· radicals in the UV light.

Jor - 21-5-2011 at 14:47

No that's impossible. You can't just precitipate all but sodium-ions or any other ion. There will always be a counter-ion in solution.

Mr. Wizard - 21-5-2011 at 16:29

Quote: Originally posted by Jor  
No that's impossible. You can't just precitipate all but sodium-ions or any other ion. There will always be a counter-ion in solution.

I agree. I was waiting for somebody better qualified to answer.

The amount of force involved with that much charge is immense. For example, the force involved in less than 1/10000 of a mole involves about a coulomb of electrons ( 1 ampere for 1 second) is over 9 billion Newtons (2 billion pounds) at a distance of 1 meter. It would be almost physically impossible to separate the charges due to this huge force. No material ( under conditions I know of) could withstand the force. The charges WILL be balanced.

A link to Coulombs Law.
http://kentshillphysics.net/EM2.htm

[Edited on 22-5-2011 by Mr. Wizard]