How do compounds dissolve?

1 Answer
Apr 21, 2018

Got me, just how DO compounds dissolve?


The length of time this question has been unanswered means that it is a tricky proposition to let us make a ham-fisted attempt here. We specify the solvent as water (without too much loss of generality), because this is the solvent of all biology, as well as a POTENT solvent for inorganic solutes.

For ionic solutes we conceive that bond-breaking occurs on dissolution to give solvated individual cations and anions, i.e. for #"sodium chloride"#....

#NaCl(s) stackrel(H_2O)rarrNa^+ + Cl^(-)# in solution, both the ions are solvates i.e. #Na^+(OH_2) #"aquated ions"#. Now this is quite properly considered to be a chemical reaction in that strong bonds are broken and new substances are formed; that the process is reversible is IMMATERIAL.

On the other hand, water is a capable solvent for many NON-IONIC solutes....i.e. for dioxygen...

#O_2(g) stackrel(H_2O)rarrO_2(aq)#

And without such a physical reaction, the oceans would not be able to sustain life. And the solubility of gases in water may be explained on the basis of old #"Henry's Law"#, which states that solubility of a gas in water, FOR A GIVEN TEMPERATURE, is proportional to the partial pressure of that gas above the solution...

#P_"gas"=kC_"concentration of gas in solution"#.