When does a solute form ions?

Question

If I have $\ce{HCl}$ and I put it in water, it will form ions. But, if I take $\ce{HCl}$ and put in benzene, it won't. How do you know that? If I had other substances, how would I know if it forms ions or not?

Answer 1

In water, HCl reacts to form $\ce{H3O+}$ and Cl-.

Then, water molecules surround the respective ions in a stabilizing orientation. The partially negatively charged O atoms of water interact with the $\ce{H3O+}$. The partially positively charged H atoms of water interact with the Cl-.

None of the above can occur in benzene because benzene is very reluctant to accept a proton and because benzene is non-polar.

Generally speaking, polar solvents have an ability to stabilize ions that nonpolar solvents do not.