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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: dane502 on April 04, 2008, 03:42:56 PM

Title: Solubility of bromine and iodine in water
Post by: dane502 on April 04, 2008, 03:42:56 PM

Hi.

Last year I remember making some expirments in my class with the reactions bromine water and triglycerids, bromine water and alkenes and so on. Now I got to wonder, why can bromine even dissovle in water?

To the best of my knowledge only ions and polar molecules can dissovle in water (Like dissolves like, right?), yet a thing like bromine water exists  ???

I have been trying to find an explanation on the internet, but I have not been able to find one. However, I read somewhere that iodine is NOT soluble in water, however clorine is soluble in water.

So could someone please explain to me, why the nonpolar halogen iodine is not soluble in water, while the nonpolar halogens bromine and chlorine are soluble in water?

I greatly appreciate your help
Dane502

Title: Re: Solubility of bromine and iodine in water
Post by: Arkcon on April 04, 2008, 04:34:33 PM

Just a heads up, iodine is very sparingly soluble in water.  In fact, it's solubility in water is useful for, an admittedly not particularly precise application -- the amount of iodine that will dissolve in 15 ml of water at 20 C will adequately purify 1 L of water for human consumption, it's called the Kahn-Visscher procedure, if you want to Google for references.  It's a common trick for hikers and campers.

Title: Re: Solubility of bromine and iodine in water
Post by: MrOHBrown on April 05, 2008, 05:34:15 AM

Here is my guess...

Diatomic Halogens have a lot of electrons just orbiting around with no involvement with the bonding. This increases the probability of temporary dipoles which first of all provides the molecules with some level of intramolecular bonding, albeit very weak, and it is these temporary dipoles which can attract the poles of a water molecule, allowing solubility.

Why would Iodine be less soluble? I suppose because it's temporary diploes provide such relatively high intramolecular bonding (thanks to a whole extra shell fo electrons) that it resists attack from water.

EDIT: Incorrect guess

Title: Re: Solubility of bromine and iodine in water
Post by: Borek on April 05, 2008, 06:18:36 AM

Hypochlorous, hypobromous and hypoiodous acids.

Title: Re: Solubility of bromine and iodine in water
Post by: MrOHBrown on April 05, 2008, 07:50:06 AM

Quote from: Borek on April 05, 2008, 06:18:36 AM

Hypochlorous, hypobromous and hypoiodous acids.

Ahhh, dissociation is the key...

http://en.wikipedia.org/wiki/Hypobromite

Thanks Borek