# How do compounds dissolve?

Apr 21, 2018

Got me, just how DO compounds dissolve?

#### Explanation:

The length of time this question has been unanswered means that it is a tricky proposition to address...so 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 $\text{sodium chloride}$....

$N a C l \left(s\right) \stackrel{{H}_{2} O}{\rightarrow} N {a}^{+} + C {l}^{-}$ in solution, both the ions are solvates i.e. $N {a}^{+} {\left(O {H}_{2}\right)}_{6}$...so-called $\text{aquated ions}$. 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...

${O}_{2} \left(g\right) \stackrel{{H}_{2} O}{\rightarrow} {O}_{2} \left(a q\right)$

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 $\text{Henry's Law}$, 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...

${P}_{\text{gas"=kC_"concentration of gas in solution}}$.