What happens to the ions after dissociation in an aqueous solution? [closed]

Question

I'm in high school studying about Buffer Solutions. We had an example of a solution made up of Ammonium Hydroxide and Ammonium Chloride for a Basic Buffer.

NH4OH ⇌ NH4 (+) + OH(-)

NH4Cl ⇌ NH4 (+) + Cl(-)

What is up with the reversible sign? Do the compounds, once dissolved in water, break into ions, and then form the reactants again? This is a petty doubt perhaps, but I need conceptual clarity.

Now, if I add a strong acid, the H(+) would be accepted by the OH(-) from Ammonium Hydroxide, right? But then where would the Cl(-) go?

And if I add a strong base, the OH(-) will be accepted by an Ammonium ion. What about the rest of the ions? Do they just stay suspended? Or do they react or something, and form the reactants once again?

Say, I want to mix something else in there, shouldn't it technically react and form newer compounds?

Answer 1

Atoms and radicals move all the time. In ionic solutions, they're particularly mobile, and do continually form new relationships.

Some groups are quite stable; e.g., in $\ce{NH4Cl}$ solution in water, $\ce{NH4+}$ mostly "sticks together". In solution, it is free to wander around the beaker, surrounded by a bevy of covetous negative ions. Lose the water through evaporation, however, and the $\ce{NH4+}$ and $\ce{Cl-}$ neatly form up again into a neat lattice.

Water itself is an example: $\ce{H2O <--> H+ + OH-}$ and yet other species. On the average, at room temperature, only about 2 molecules in 10⁹ are ionized, yet that still gives it a somewhat ionic character.

Viewing an animation of salt dissolving in water might help you visualize the process.