MadSci Network: Chemistry
Query:

Re: What types of elements does water mix with the best?

Date: Sun Jan 9 08:11:20 2000
Posted By: David Barker, Grad student, Organic Chemistry, University of Sydney
Area of science: Chemistry
ID: 946935895.Ch
Message:

This question isn't as easy as you might think to answer because solubility is quite a complex concept.

The first thing you should think of is why do chemicals like salt and baking soda dissolve in water at all, lots of chemicals such as oils do not dissolve.

An easy rule to remember is "Like dissolves like". Now while you probably don't know this but chemists think of water as charged, it is made up of positive and negative charges. This is the reason electricity goes through water. Now salt, which is really the chemical sodium chloride, is also charged. Salt is made up of charged sodium atoms and charged chlorine atoms so these are kind of like the charged water, so thats why salt dissolves in water.

Baking soda is really the chemical sodium bicabonate and it too is charged, it is made up of charged sodium atoms and charged bicarbonate molecules, so it too dissolves in water. Neither salt or baking soda, like water, would dissolve in oil, as oil is totally uncharged, try this one if you want too.

We determine the solubilty chemicals by looking at the solubility of all the components of the chemical and working out a "Solubility Product" for that chemical. So for salt this would look something like this :

Solubility Product of Salt = (concentration of sodium atoms) X (concentration of chlorine atoms).

So the solubility of a chemical is determined by the solubility of the molecules and atoms that make up that chemical.

So when it comes to the solubility of salt vs baking soda, this is determined by how well the salt molecules break up in the water vs how well the baking soda molecules break up and how well each of the atoms "like" the water they are in and how much of it dissolves.

In this case salt breaks up more easily than baking soda and the chlorine atoms from salt interact better with water than the bicarbonate molecules from baking soda do with water. So salt is more soluble than baking soda.

Well I hope you could understand all that, solubility is a very complicated topic, that has lots of things to consider, hope my answer was of assistance.

regards

David Barker


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